PREFACE

There is no work in the English language dealing with the Reptiles of Europe. I have therefore endeavoured to supply this desideratum, so far as the Snakes are concerned, by drawing up in a concise form an account of what is known of their characters, their distribution, and their life-histories. Professor Sordelli, of Milan, having kindly acceded to my request to reproduce some of the beautiful figures drawn by him for the work published in collaboration with the late Professor Jan under the title of “Iconographie Générale des Ophidiens,” I have been able to supplement my descriptions with illustrations which leave nothing to be desired from the point of view of accuracy. A few drawings have been made specially for this book by Mr. J. Green. I have further to acknowledge the permission given by the Trustees of the British Museum, the India Office, and the Zoological Society, to reproduce a few figures from previous publications of which I am the author.

In order to render this little book more useful, the account of the Snakes of Europe has been preceded by an Introduction summarizing what is known of Snakes generally.

I have purposely avoided overburdening a work of this kind, which aims at concision, with bibliographical references and synonymic lists. I am sure my readers will be thankful for being spared this display of erudition. Whenever I have had to compile, and to trespass on ground that is not my own, I have been careful to draw only from the writings of the most trustworthy authorities. The descriptions of the species are based on the collection in the British Museum, which has been considerably increased since the publication of the Catalogue of Snakes (1893-1896). I have also had access to Monsieur F. Lataste’s rich private collection, now under my care, and Dr. R. Gestro has kindly entrusted to me for study the collection of Italian Snakes in the Genoa Museum. I am indebted to Dr. L. W. Sambon for the chapter on Parasites, which he has written at my request.

To all who have helped me I beg to tender my hearty thanks.

G. A. B.

CONTENTS

INTRODUCTION
CHAPTERPAGE
I.Definition and Classification[1]
II.External Characters—Integument[8]
III.Coloration[29]
IV.Skeleton[40]
V.Dentition[53]
VI.Poison Apparatus—Different Kinds of Poisons[62]
VII.Nervous System-Sense Organs[73]
VIII.Viscera[77]
IX.Organs of Reproduction; Pairing; Oviposition; Development[82]
X.Habits[91]
XI.Parasites[107]
XII.Distribution[118]
XIII.Snakes in Relation to Man[133]
SYSTEMATIC ACCOUNT OF THE SNAKES
OF EUROPE
First Family: TYPHLOPIDÆ
Genus TYPHLOPS, Schneider[144]
1.Typhlops vermicularis, Merrem—The Greek Blind-Snake[144]
Second Family: BOIDÆ
Genus ERYX, Daudin[147]
2.Eryx jaculus, Linnæus—The Javelin Sand-Boa[147]
Third Family: COLUBRIDÆ
Genus TROPIDONOTUS, Kuhl[152]
3.Tropidonotus natrix, Linnæus—The Grass-Snake,
or Ring-Snake[152]
4.Tropidonotus tessellatus, Laurenti—The Tessellated
Water-Snake[160]
5.Tropidonotus viperinus, Latreille—The Viperine
Water-Snake[165]
Genus ZAMENIS, Wagler[170]
6.Zamenis gemonensis, Laurenti—The European Whip-Snake[170]
7.Zamenis dahlii, Fitzinger—Dahl’s Whip-Snake[177]
8.Zamenis hippocrepis, Linnæus—The Horseshoe Whip-Snake[179]
Genus COLUBER, Linnæus[181]
9.Coluber quatuorlineatus, Lacepède—Aldrovandi’s Snake[182]
10.Coluber dione, Pallas—The Dione Snake[185]
11.Coluber longissimus, Laurenti—The Æsculapian Snake[187]
12.Coluber leopardinus, Bonaparte—The Leopard Snake[191]
13.Coluber scalaris, Schinz—The Ladder Snake[194]
Genus CORONELLA, Laurenti[196]
14.Coronella austriaca, Laurenti—The Smooth Snake[197]
15.Coronella girondica, Daudin—The Southern Smooth Snake[202]
Genus CONTIA, Baird and Girard[205]
16.Contia modesta, Martin—The Dwarf Snake[205]
Genus CŒLOPELTIS, Wagler[207]
17.Cœlopeltis monspessulana, Hermann—The Montpellier Snake[208]
Genus MACROPROTODON, Guichenot[212]
18.Macroprotodon cucullatus, I. Geoffroy—The False
Smooth Snake[213]
Genus TARBOPHIS, Fleischmann[216]
19.Tarbophis fallax, Fleischmann—The Cat-Snake[217]
20.Tarbophis iberus, Eichwald—The Caucasian Cat-Snake[219]
Fourth Family: VIPERIDÆ
Genus VIPERA, Laurenti[221]
21.Vipera ursinii, Bonaparte—Orsini’s Viper[221]
22.Vipera renardi, Christoph—Renard’s Viper[227]
23.Vipera berus, Linnæus—The Northern Viper, or Adder[230]
24.Vipera aspis, Linnæus—The Asp Viper[239]
25.Vipera latastii, Bosca—Lataste’s Viper[247]
26.Vipera ammodytes, Linnæus—The Sand-Viper, or
Long-Nosed Viper[249]
27.Vipera lebetina, Linnæus—The Blunt-Nosed Viper, or Kufi[257]
Genus ANCISTRODON, Palisot de Beauvois[261]
28.Ancistrodon halys, Pallas—Pallas’s Pit-Viper[262]
Index[265]

LIST OF PLATES

PLATEFACING PAGE
I.Typhlops vermicularis, Eryx jaculus[144]
II.Tropidonotus natrix and Vars. cettii and persa[152]
III.Tropidonotus tessellatus, T. viperinus and
var. aurolineatus[160]
IV.Zamenis gemonensis and vars. persica and
viridiflavus[170]
V.Zamenis gemonensis, var. caspius, Z. dahlii,
Z. hippocrepis[176]
VI.Coluber quatuorlineatus and var. sauromates,
C. dione[182]
VII.Coluber longissimus, C. leopardinus and
var. quadrilineatus[188]
VIII.Coluber scalaris[194]
IX.Coronella austriaca[196]
X.Coronella girondica, Contia modesta[202]
XI.Cœlopeltis monspessulana, Macroprotodon
cucullatus, Tarbophis iberus, T. fallax[208]
XII.Vipera ursinii, V. renardi, V. berus[220]
XIII.Vipera aspis, V. latastii[240]
XIV.Vipera lebetina, V. ammodytes, Ancistrodon halys[250]

THE SNAKES OF EUROPE

INTRODUCTION

CHAPTER I
DEFINITION AND CLASSIFICATION

Snakes, Ophidia—regarded by some authorities as an order of the class Reptilia, by the author as a sub-order of the order Squamata, which includes besides the Lizards, Lacertilia, the Chameleons, Rhiptoglossa, and the extinct Dolichosauria and Mosasauria—may be defined as greatly elongate scaly Reptiles without limbs, or with mere vestiges of the hind pair, without movable eyelids, without ear-opening, with elongate, deeply forked tongue retractile into a basal sheath, with transverse vent and paired copulatory organs, and with the two halves of the lower jaw independently movable, connected at the symphysis by an elastic ligament.

The latter character alone distinguishes them from all Lizards, but no single Lizard possesses all the others in combination.

In their most highly developed form these Reptiles are adapted for rapid reptation and for swallowing prey much exceeding their own calibre; hence the bones of the skull, on which a prehensile function devolves, are loosely attached to the cranium by ligamentous elastic tissue, or articulated in such a manner as to permit a wide buccal expansion; whilst the absence of a sternum and the mobile attachment of the ribs allow a corresponding dilatation of the body as the prey descends into the digestive canal.

The fatal venom which many of these Reptiles possess has so impressed the mind of men, even the scientific, that for a long time snakes were primarily divided into poisonous and non-poisonous, a classification in which the more important characters, derived from the general structure, and especially from the skull, were subordinated to the physiological. Such a system was far from reflecting natural relationships. Besides, as our knowledge progressed, drawing a distinction between poisonous and harmless snakes became more and more difficult, so many snakes previously regarded as harmless proving to be poisonous in various degrees—at least enough to paralyze the small prey on which they subsist, if not to be of serious danger to man.

In the division into families, as followed in this work, the presence or absence of a poison organ is left out of consideration. Further, in this as in many other groups of the animal kingdom, external characters do not furnish trustworthy indications for higher divisions, and the definitions of the families are therefore based exclusively on osteological characters. For those who wish to name snakes with facility, the key which concludes the chapter on External Characters will, however, remedy this defect, and suffice for the identification of all the European species without any reference to their anatomy. Many attempts have been made to furnish an easy criterion for the distinction of harmless from poisonous snakes, but the characters hitherto suggested with this object can only be applied successfully to the small number of representatives in a limited area. Thus, in Southern Australia it might be stated that all snakes showing the regular nine large shields on the upper surface of the head are dangerous to man, whilst those with small shields or scales are harmless; but in most parts of Europe this criterion would have to be reversed. In some countries the shape of the pupil might be used for the purpose, in others the size of the ventral shields, or the presence or absence of a loreal shield, between the nasal and the preocular, and so on. But when we have to deal with the snakes of the whole world, about 2,000 species, of which nearly one-third are poisonous to a greater or less degree, every attempt at a definition of the two categories without regard to the dentition breaks down. Only those who have made a study of the snakes of the world can make a guess from the general appearance as to an unknown form being poisonous or not, and even they may sometimes feel embarrassed, unless the dentition be examined; the mistakes which have occasionally been made by some experienced herpetologists are proof sufficient of the fallacy of external characters for this purpose.

The Ophidia are divided into nine families, the first, third, seventh, and ninth of which have representatives in Europe:

I. No transverse (ectopterygoid) bone; pterygoid not extending to quadrate or mandible; no supratemporal; nasals in contact with prefrontals; coronoid present; vestiges of pelvis.

Maxillary loosely attached to lower surface of cranium, toothed; lower jaw edentulous; a single pelvic bone

1. Typhlopidæ.

Maxillary bordering mouth, forming a suture with premaxillary, prefrontal, and frontal, toothless; pubis and ischium present, latter forming a symphysis

2. Glauconiidæ.

II. Transverse bone present; both jaws toothed.

A. Coronoid present; nasals in contact with prefrontals.

1. Vestiges of pelvis; supratemporal present.

Supratemporal large, suspending quadrate

3. Boidæ.

(Subfamilies: Pythoninæ, Boinæ.)

Supratemporal small, intercalated in the cranial wall

4. Ilysiidæ.

2. No vestiges of pelvis; supratemporal absent

5. Uropeltidæ.

B. Coronoid absent; supratemporal present.

1. Maxillary horizontal; pterygoids reaching quadrate or mandible.

Nasals in contact with prefrontals

6. Xenopeltidæ.

Nasals not in contact with prefrontals

7. Colubridæ.

Three series: A. Aglypha (subfamilies: Acrochordinæ, Colubrinæ, Dasypeltinæ); B. Opisthoglypha (Homalopsinæ, Dipsadomorphinæ, Elachistodontinæ); C. Proteroglypha (Hydrophiinæ, Elapinæ).

2. Maxillary horizontal, converging posteriorly towards palatine; pterygoid not reaching quadrate or mandible

8. Amblycephalidæ.

3. Maxillary vertically erectile perpendicularly to transverse bone; pterygoid reaching quadrate or mandible

9. Viperidæ.

(Subfamilies: Viperinæ, Crotalinæ.)

The technical terms employed in the above synopsis will be found explained and illustrated by figures in the chapter on the Skeleton.

No serial arrangement can express the affinities of the various groups as conceived by the classificator; a diagram therefore follows to show the author’s views as to their interrelationships, and possibly their phylogeny. Leaving aside the Typhlopidæ and Glauconiidæ, which should be regarded as burrowing types independently derived from some Ophidian form less specialized than any with which we are at present acquainted, and probably without direct relationship to the Lizards, the family Boidæ, and more especially the Pythons, claim the position of ancestral group, from which all other snakes may have been derived.

Viperidæ Amblycephalidæ
Colubridæ opisthoglyphæ Colubridæ proteroglyphæ
Uropeltidæ
IlysiidæXenopeltidæColubridæ aglyphæ
Boidæ

Further remarks on this subject in the chapter on Dentition.

It is to be regretted that paleontology cannot help us at present as concerns the lines of evolution, the comparatively few fossil Ophidians known, from the Lower Eocene upwards, the remains of which can be identified with some measure of certainty, being either non-poisonous types (Boidæ, Ilysiidæ, Palæophiidæ, Colubridæ) or Viperidæ (Viperines from the Miocene of France and Germany, Crotalines from the Miocene of North America). The vertebræ from the Puerco Eocene of America, on the limit between the Cretaceous and Eocene periods, described as the oldest snake remains, Helagras, Cope, are stated to approach the Lacertilian type.

Whether the vertebræ named Symoliophis, Sauvage, from the chalk of France, and Coniophis, Marsh, from the Laramie Cretaceous of North America, are Ophidian, as claimed by their describers, or Dolichosaurian, cannot be decided without further material.

CHAPTER II
EXTERNAL CHARACTERS—INTEGUMENT

The form varies enormously, worm-like in some, comparatively short and heavy, elongate and more or less slender, or extremely gracile and almost filiform, in others. In this respect our common Grass-snake occupies a central position, and for this reason is termed a moderately slender form, anything above or below this standard being described as comparatively short or elongate. Our shortest and stoutest European Snakes are the Vipers, especially Vipera ursinii; our longest and slenderest, the Coluber and Zamenis, especially Zamenis dahlii. These extremes in both directions are, however, far surpassed by many exotic snakes, as we find on comparing, for instance, one of the African Puff-adders (Bitis), with certain Oxybelis and Leptognathus from Tropical America. The body may be somewhat rigid, as in some burrowing and ground snakes, not unlike in appearance to our Slow-worm and other limbless Lizards; or extremely flexible, as in many Pythons and Boas and in the Tree-snakes generally. This flexibility may be accompanied by a vertical compression of the body in relation with an arboreal existence, whilst sluggish snakes, such as most of the Viperidæ, may be remarkable for the flattening of the body, which they may further increase when basking in the sun or in order to assume a more formidable appearance on the approach of an enemy. This power of flattening out the whole or the anterior part of the body is possessed by many snakes, poisonous as well as harmless, and reaches its highest degree in the Cobras of India and Africa, the expanded anterior part being known as the “hood,” from the Portuguese name “Cobra di capello.”

Thoroughly aquatic snakes are often short and heavy, but some of the marine forms, or Hydrophids, may be extremely slender, with the posterior part of the body compressed. In some of these Sea-snakes the gracility of the anterior part, or “neck,” as it has been called, contrasts very strikingly with the great girth of the body towards the tail, and suggests a limbless Plesiosaur.

The tail, the part of the body behind the transversely cleft vent, is most frequently about one-fourth or one-fifth of the total length; but it may be much shorter, even reduced to a mere stump, as in the Typhlops, or, at the opposite extreme, enter for one half in the length of the snake, as in the African Xenurophis. This organ may taper gradually to a fine point; or end abruptly, as if mutilated; or terminate in a horny spine, such as we see in some of the Typhlops or in the Australian Death-adder, Acanthophis, or in a series of horny segments which are vibrated like a rattle, as in the well-known Crotalus of America, to which we shall refer again at the end of this chapter. In some of the burrowing Uropeltidæ, the very short tail is obliquely truncated, with indurated shields above, and acts as a trowel. And, finally, the marine snakes of the subfamily Hydrophiinæ are distinguished by a strongly compressed, oar-shaped tail, with rounded vertical outline. In a few forms, arboreal or aquatic, the tail is more or less prehensile.

Males generally have a longer tail than females, and the genital organs, which are lodged in its base, cause a swelling of that region which contrasts with the more gradually tapering extremity of the female, thus affording a means of distinguishing the sexes externally in the majority of snakes.

The rudimentary hind limbs of Boid snakes, to be mentioned further on in the description of the skeleton, terminate in a claw-like horny spur, which appears on each side of the vent in the male, and sometimes also, though less distinctly, in the female. These spurs are probably of use in facilitating the pairing, an explanation which appears the more plausible from the fact that the snakes provided with them have the copulatory intromittent organs destitute of the erectile spines which are present in most others.

The head varies in shape as much as the body. Although never actually compressed, except in the rostral region, it may be very narrow and elongate, whilst in the opposite extreme it may be strongly depressed, and so broad behind as to be abruptly defined from the anterior part of the body, or “neck.” This feature is very marked in some of the Viperidæ, and this has given rise to the incorrect generalization that poisonous snakes are distinguished from the harmless by a broad and flat head, notwithstanding the fact that some of the most dangerous, such as the Mambas, Cobras, and Kraits, have a comparatively narrow or small head, not or but slightly defined behind, whilst, on the other hand, the very opposite condition obtains in not a few of the harmless Colubrids.

Leaving the Typhlopidæ and Glauconiidæ aside for the present, snakes have a wide gape, cleft far beyond the vertical of the eyes, with, when closed, one or two notches in front for the passage of the protrusible, bifid tongue. In most snakes this chink is in the lower border of the rostral shield, capping the tip of the snout, and allows free passage to the whole tongue; in the Hydrophids, or Sea-snakes, there are two notches in the lower border of the rostral shield, through which only the bifid end of the tongue can be protruded. The eyes, varying from minute to enormous, are usually free from the surrounding shields, and may move under a transparent cap like a watch-glass, which appears to represent the lower eyelid of Lizards. The view as to this homology is derived from our knowledge of various conditions in certain series of Lizards of the families Lacertidæ and Scincidæ, where we find a transparent disc appearing like a small window in the movable lower eyelid, gradually increasing in size so as to occupy the whole of the lower eyelid, which finally becomes fused with the rudimentary upper lid and loses its mobility. In Ilysia and in most of the Uropeltidæ, the transparent disc over the eye is confluent with a thick horny shield of which it occupies the middle.

The pupil is usually circular or vertical, rarely horizontal. In some forms it is difficult to decide whether it is round or vertically elliptic; in others, like the Boas and Vipers, for instance, it is decidedly vertical, and contracts to the same extent as a cat’s. In some Water-snakes, and in Sea-snakes generally, the round pupil may contract to a mere dot. The contraction of the pupil is independent on the two sides.

The snout, or the part of the head anterior to the eyes, may be short or long, rounded or pointed, depressed or compressed, sometimes projecting strongly beyond the mouth, turned up at the end, or terminating in one (Langaha) or two (Herpeton) long scaly dermal appendages. In some burrowing forms it is provided with a more or less trenchant horizontal or vertical edge. When the sides of the snout (loreal region) form an angle with the upper surface, the angle is termed the “canthus rostralis,” which may be intensified by the loreal region being concave.

The deep pits which are sometimes present on the lips or between the nostril and the eye (loreal pit) will be alluded to further on under Sensory Organs.

The nostrils are either lateral, or, in the aquatic forms, directed upwards, sometimes entirely on the upper surface of the snout.

Most snakes have a longitudinal groove on the chin (mental groove) to allow for the distension caused by the lateral movements of the rami of the lower jaw.

In the Typhlopidæ, the head passes gradually into the vermiform body, and the small mouth is situated on the under surface of the projecting snout; the head so resembles the extremely short tail, and the mouth is so similar in shape and position to the vent, which is close to the posterior extremity of the snake, that such creatures are often believed by non-critical observers to have a head at each end. The eyes are very small, and covered over by the semi-transparent head-shields, or they may be completely concealed. There is no mental groove. It is much the same with the Glauconiidæ, which have, however, a somewhat less abbreviated tail. In both, the nostrils often open on the lower side of the snout, which may be excavated so as to appear hooked in profile, or may be provided with a sharp cutting horizontal edge.

Snakes are covered with epidermal folds in the form of scales and shields, the shape and arrangement of which affords important characters for their classification. Dermal ossifications are absent.

The scales on the body are usually elliptic or lanceolate and imbricate, forming straight longitudinal and oblique transverse series, and they are replaced on the belly and under the tail by transverse shields mostly corresponding in number with the series of scales, and also with the vertebræ. The body of the Typhlopidæ and Glauconiidæ is uniformly covered with polished, closely adherent, rounded, overlapping, sub-equal scales, without even an indication of ventral shields. In some of the Acrochordinæ, aberrant aquatic Colubrids, the scaling consists, above and beneath, of small juxtaposed, sometimes spinose granules, the skin being suggestive of the shagreen of sharks. In the marine snakes of the subfamily Hydrophiinæ, the ventral shields are often absent or merely indicated, and the scales are mostly juxtaposed or feebly imbricate, sometimes tetragonal or hexagonal, and occasionally studded with spinose tubercles. In the more typical Ophidia the imbricate scales may be long and narrow or short and broad, with every intermediate step between the two extremes; smooth or furnished with a longitudinal ridge or keel, or even several keels; nearly equal in size or with the median or outer series more or less enlarged, the longitudinal series in odd, rarely in even number; instead of running in longitudinal series parallel with the axis of the body, as is the rule, they are sometimes disposed obliquely, and among those in which we meet with this peculiarity several genera are further remarkable in having some of the oblique lateral scales furnished with a serrated keel, to which we shall again allude in the chapter on Habits, when dealing with the rustling sounds produced by certain snakes. The number of longitudinal series of scales on the body varies from 10 (Herpetodryas) to nearly 100 (Python, Boa); in the European species from 17 (Contia modesta) to 50 (Eryx jaculus). The scales are sometimes furnished near the end with one or two shallow impressions, termed “apical pits,” which afford indications for the distinction of genera and species; unless of a lighter or darker colour, as is often the case, these pits are not always easy to see, except in a strong light and with the aid of a powerful magnifying glass.

The ventral shields, also called “gastrosteges,” usually occupy the whole width of the belly; but they may be much narrower—in Eryx, for instance. They are sometimes bent at an angle on the sides, and this angle may even form a sharp keel, accompanied by a notch in the posterior border, corresponding to the keel, as in several of the more arboreal genera of Colubrids. The shields under the tail, termed subcaudals or “urosteges,” are sometimes similar to the ventrals, but more often disposed in pairs; in certain species or individuals some of the subcaudals are single, and the others paired. When the number of subcaudals is given in the descriptions, each pair is reckoned as one, and the conical or spine-like shield which caps the end of the tail is not included. These numbers afford important characters for the definition of species, and sometimes also for the distinction of sexes. The subcaudals are nearly always much fewer than the ventrals, but the difference is often not so great in the males as in the females, the tail of which is usually shorter in proportion to the body. It is noteworthy that in many species, if the number of subcaudals (C.) be added to that of the ventrals (V.), the total is nearly the same in the male as in the female, however much the respective numbers may differ when taken separately. The following figures may be given by way of example, taken from British specimens:

Coronella austriaca:♂V. 154;C. 58 = 212
Coronella austriaca:♀V. 165;C. 48 = 213
Vipera berus:♂V. 138;C. 35 = 173
Vipera berus:♀V. 144;C. 29 = 173

Although this rule is by no means universal, and does not apply at all to some species, it will be found to hold good in many cases, and is of interest in showing that the changes that have taken place in the vertebral column (the vertebræ corresponding in number to the shields), according to the sexes, have been by a modification of the character of the segments about the anal region, a conversion of trunk vertebræ into caudals, or vice versa. In dealing with certain species—of Vipers, for instance—it is important, for systematic purposes, to keep the counts of shields distinct for the two sexes.

The shield which covers the vent, the anal shield, is either single or divided into two.

Some snakes have the head covered with scales or small tubercles similar to those on the body, but in the great majority the lepidosis is in the form of large symmetrical juxtaposed shields, the shape, proportions, and number of which furnish some of the most important characters for the distinction of genera and species. These head-shields belong to two primarily different types, from each of which all further modifications may be regarded as derived by alteration in shape or by disintegration. The first type is that shown by the Typhlopidæ and Glauconiidæ, which is explained by the figure on the next page.

The rostral, which is usually the largest of the head-shields, extends to the upper surface of the head, of which it may occupy the greater part. In the Glauconiidæ, the ocular usually borders the mouth.

As may be seen by a comparison of the first figure with the second, the arrangement of the head-shields is essentially different from that which prevails in the Colubrids and the majority of other snakes.

The second type is exemplified by the head of a member of the genus Zamenis.

In the descriptions, temporals 2 + 3 means two superposed temporals in the first row, three in the second. The internasals and the temporals, and the loreal and the preocular, are sometimes absent, and the prefrontal or the internasal may be single. One or two large shields are in rare cases present behind the parietals, and are called occipital.

Fig. 1—Head of Typhlops braminus. (From “Fauna of British India”)

f, Frontal; ip, interparietal; l, labial; n, nasal; o, ocular; p, parietal; po, preocular; prf, prefrontal; r, rostral; so, supraocular.

A breaking up into smaller shields takes place in many snakes. In the Pythons, for instance, the frontal may be divided into two by a longitudinal cleft, and separated from the prefrontals by small shields. In some Vipers, such as V. berus and V. ursinii, in which the frontal and parietals, though reduced in size, usually preserve their primitive condition, the former is normally separated from the supraocular by a series of small shields, and the internasals and prefrontals are broken up; in these snakes the small shield or shields behind the rostral are termed “apical,” and those on the upper edge of the snout are termed “canthals.” The shield which, in Vipers, separates the rostral from the nasal is called “naso-rostral.” Allusion has been made above to the scaly dermal appendages which terminate the snout in certain genera. Some Viperidæ are furnished with horn-like erect spines above the eyes or at the end of the snout, which add greatly to their sinistral appearance.

Fig. 2—Head of Zamenis ventrimaculatus. (From “Fauna of British India”)

cs, Chin-shields (anterior); cs´, chin-shields (posterior); f, frontal; in, internasal; l, loreal; la, labial (upper); la´, labial (lower); m, mental; n, nasal; p, parietal; pf, prefrontal; pro, preocular; pto, postocular; r, rostral; sbo, subocular; so, supraocular; t, temporals (first row); t´, temporals (second row); v, first ventral.

The periodical shedding of the outer layer of the epidermis in a single piece, including even the covering of the eye, is one of the most striking peculiarities of snakes, although paralleled in the Lizards of the family Anguidæ, to which our British Slow-worm belongs. The skin becomes detached at the lips, and is turned inside out from head to tail, without any sort of laceration when the snake is in good health. These exuviæ are transparent, but often carry a certain amount of pigment, especially those of the Vipers, in which the characteristic dark markings are perfectly visible; they usually exceed the length of the reptile, owing to stretching. In Sea-snakes the epidermis is cast piecemeal, and sloughing is a longer operation than in ordinary snakes.

In Rattlesnakes each piece of the rattle, or “crotalon,” in which the tail terminates, represents a retained portion of the sloughed epidermis. This remarkable appendage looks like a number of horny rings, but it consists in reality of hollow, bell-like pieces, similar to the terminal one, or “button,” each with a circular constriction, in which the incurved free edge of the following piece fits, thus keeping the pieces together without impairing the mobility necessary to produce the rattling sound for which the apparatus is intended. At each exuviation one bell-shaped horny piece is added. The number of segments in the rattle is, therefore, not an index to age, as formerly believed; nor is it to the number of exuviations, for whilst segments are being added at the base of the apparatus the terminal ones break off and are lost. A Crotalus sixteen months old may have six pieces to the rattle if there have been six exuviations and no loss. No rattle appears ever to comprise more than about twenty pieces, even in old specimens. The size of the terminal button shows whether it was formed at birth or at any later period, no growth taking place in the horny tissue.

So far as trustworthy records are concerned, the largest snakes known, the Malay Python reticulatus and the South American Anaconda, Eunectes murinus, reach a length of 25 to 30 feet. Measurements of skins must be accepted with caution, as a skin may easily be stretched to once and a half its real length; in estimating the exact length from such a stretched skin, it is necessary to deduct the interstitial spaces showing between the scales, and about one-fourth of the scale to allow for the overlap. The smallest snake known is 4 inches long (Glauconia dissimilis). The largest European snake (Coluber quatuorlineatus) is reported to reach a length of 8 feet; the smallest (Typhlops vermicularis) does not exceed 14 inches.

Key to the Identification of the European Snakes from External Characters only

I. Eyes minute, under the head-shields; mouth small, inferior; body vermiform, covered with uniform scales above and beneath; vent close to the end of the body, the extremely short tail ending in a small spine

Typhlops vermicularis.

II. Eyes very small, with vertical pupil; upper surface of head covered with small scales; ventral shields much narrower than the body; tail short, ending obtusely; subcaudals single, or mostly single; scales smooth or feebly keeled, in 40 to 50 rows

Eryx jaculus.

III. Eyes small, moderate, or large; ventral shields at least nearly as broad as the body; tail tapering to a point; subcaudals paired.

A. Pupil round; upper surface of head with nine large shields; no upper labial in contact with the parietal; anal shield usually divided.

1. Dorsal scales strongly keeled, with paired apical pits; a single anterior temporal.

a. Nostrils lateral; internasals broadly truncate in front.

Scales in 19 rows; normally 1 pre- and 3 postoculars; usually 7 upper labials, third and fourth entering the eye; ventrals 157-181; subcaudals 50-88

Tropidonotus natrix.

b. Nostrils directed upwards; internasals much narrowed in front.

Scales in 19 rows; normally 2 pre- and 3 or 4 postoculars; suboculars sometimes present; usually 8 upper labials, fourth or fourth and fifth entering the eye; ventrals 160-187; subcaudals 48-79

Tropidonotus tessellatus.

Scales in 21 (rarely 19 or 23) rows; normally 1 or 2 pre- and 2 postoculars; usually 7 upper labials, third and fourth entering the eye; ventrals 147-164; subcaudals 46-72

Tropidonotus viperinus.

2. Dorsal scales smooth or feebly keeled; normally a single loreal.

a. Two or three superposed anterior temporals (very rarely one); nostril usually between two nasals.

α. A subocular below the preocular.

* Scales smooth, in 17 or 19 rows.

Two upper labials entering the eye; preocular not in contact with the frontal; scales with two apical pits; ventrals more or less distinctly angulate laterally, 160-230; subcaudals 87-131

Zamenis gemonensis.

Two upper labials entering the eye; preocular usually in contact with the frontal; scales with a single apical pit; ventrals very distinctly angulate laterally, 205-218; subcaudals 98-132

Zamenis dahlii.

** Scales in 23 to 29 rows (usually 25 or 27), with two apical pits.

Upper labials usually separated from the eye by a series of suboculars; preocular in contact with the frontal; scales smooth; ventrals very distinctly angulate laterally, 222-258; subcaudals 77-107

Zamenis hippocrepis.

Two upper labials entering the eye; preocular not in contact with the frontal; scales feebly but distinctly keeled; ventrals not angulate laterally, 195-234; subcaudals 56-90

Coluber quatuorlineatus.

Two upper labials entering the eye; preocular not in contact with the frontal; scales smooth or faintly keeled; ventrals not or but very obtusely angulate laterally, 172-214; subcaudals 50-80

Coluber dione.

β. No subocular; scales smooth, or faintly keeled on the posterior part of the body.

* Ventrals more than 200; scales with two apical pits.

Snout obtuse; rostral broader than deep; scales in 21 or 23 rows; ventrals distinctly angulate laterally, 212-248; subcaudals 60-91

Coluber longissimus.

Snout obtuse; rostral broader than deep; scales in 25 or 27 rows; ventrals not angulate laterally, 222-260; subcaudals 68-90

Coluber leopardinus.

Snout pointed, strongly projecting; rostral deeper than broad, wedged in between the internasals; scales in 25 to 29 rows; ventrals not angulate laterally, 201-220; subcaudals 48-68

Coluber scalaris.

** Ventrals not more than 200; scales mostly with a single apical pit.

Rostral at least as deep as broad, often wedged in between the internasals; usually 7 upper labials, third and fourth entering the eye; scales in 19 (rarely 21) rows; ventrals 153-199; subcaudals 41-70

Coronella austriaca.

Rostral broader than deep; usually 8 upper labials, fourth and fifth entering the eye; scales in 21 (rarely 19 or 23) rows; ventrals 170-200; subcaudals 49-72

Coronella girondica.

b. A single anterior temporal; nostril in a single nasal; scales smooth, with single apical pits, in 17 rows; ventrals 150-191; subcaudals 53-78

Contia modesta.

3. Scales longitudinally grooved in the adult, in 17 or 19 rows; two loreals; canthus rostralis strongly marked; frontal very narrow, in contact with the preocular; ventrals 160-189; subcaudals 68-102

Cœlopeltis monspessulana.

B. Pupil vertical or vertically subelliptic (sometimes appearing round in Macroprotodon).

1. Scales smooth, mostly with single apical pits; upper surface of head with nine large shields.

Frontal 11⁄2 to 2 times as long as broad; loreal separated from the eye by the preocular; one upper labial usually in contact with the parietal; scales in 19 to 23 (rarely 25) rows; ventrals 153-192; anal divided; subcaudals 40-54

Macroprotodon cucullatus.

Frontal 11⁄4 to 11⁄2 times as long as broad, much shorter than the parietals; loreal entering the eye; scales oblique, in 19 or 21 rows; ventrals 186-222; anal divided; subcaudals 48-73

Tarbophis fallax.

Frontal 11⁄4 to 11⁄2 times as long as broad, nearly as long as the parietals; loreal entering the eye; scales oblique, in 19 or 21 rows; ventrals 203-235; anal entire; subcaudals 54-70

Tarbophis iberus.

2. Scales keeled, with two apical pits; anal shield entire.

a. No pit between the nostril and the eye; upper head-shields small, if present; nasal separated from the rostral by a naso-rostral; eye separated from the upper labials by suboculars.

α. Snout not turned up at the end; supraocular usually extending posteriorly beyond the vertical of the posterior border of the eye; frontal and parietal shields usually well developed; usually a single series of scales between the eye and the upper labials.

Snout obtusely pointed, flat above, or with the canthus slightly raised; rostral usually in contact with a single apical shield, rarely with two; 6 to 9 upper labials, usually 7 or 8; scales in 19 rows, rarely 21; ventrals: ♂ 120-135, ♀ 125-142

Vipera ursinii.

Snout pointed, with raised canthus; rostral in contact with a single apical shield; 8 or 9 upper labials; scales in 21 rows, rarely 19; ventrals: ♂ 130-148, ♀ 130-150

Vipera renardi.

Snout truncate or broadly rounded, flat above or with slightly raised canthus; rostral in contact with two apical shields, rarely with one; 8 or 9 upper labials; scales in 21 rows, rarely 19 or 23; ventrals: ♂ 132-150, ♀ 132-158

Vipera berus.

β. Snout usually more or less turned up at the end or produced into a scaly dermal appendage; supraocular not extending posteriorly beyond the vertical of the posterior border of the eye; frontal and parietals often absent or very small; 2 or 3 series of scales between the eye and the upper labials; 9 to 13 upper labials; scales in 21 or 23 rows, rarely 19 or 25.

Snout simply turned up, the raised portion bearing 2 or 3 scales; rostral not more than once and a half as deep as broad; ventrals: ♂ 134-158, ♀ 141-169

Vipera aspis.

Snout simply turned up or produced into a small appendage, the raised portion with 5 or 6 (rarely 3) scales; rostral 11⁄2 to 2 times as deep as broad; ventrals: ♂ 125-146, ♀ 135-147

Vipera latastii.

Snout produced into an appendage covered with 10 to 20 scales; rostral not reaching the summit of the rostral appendage; ventrals: ♂ 133-161, ♀ 135-163

Vipera ammodytes.

γ. Snout not turned up at the end; supraocular narrow or broken up into several small shields; upper surface of head with small, usually keeled scales; two or three series of scales between the eye and the upper labials; scales in 23 to 27 rows, usually 25; ventrals: ♂ 151-177, ♀ 153-180

Vipera lebetina.

b. A pit between the nostril and the eye; upper surface of head with 9 large shields; nasal in contact with the rostral; third upper labial entering the eye; scales in 23 rows; ventrals 149-174; subcaudals 31-44

Ancistrodon halys.

CHAPTER III
COLORATION

In dealing with the coloration, we have first to distinguish between the colour and the markings. The former is very often highly variable among snakes of the same species, to say nothing of the changes which may take place with age or with the condition of the individuals, whether before or after exuviation; it is not unusual to find among specimens from the same locality a great range of variation, from greyish-white to brown, or red, or black, as, for instance, in our Common Viper. The latter afford more important characters, and often furnish valuable indications for the distinction of species; but even the disposition of the markings is subject to great individual variations, more likely to mislead than to help the inexperienced student in the discrimination of species. It is therefore always advisable to resort in the first instance to structural characters for the purpose of specific identification, and to fall back on coloration only as a means of confirmation. If we were to be guided by colour and markings alone, how could we believe that an adult four-lined Coluber quatuorlineatus is of the same species as the handsomely spotted Coluber sauromates; and yet, if we compare the young of these two snakes we find them to be absolutely identical in their markings, and, in the absence of any structural differences, we are forced to conclude that they only represent two forms of the same species, of which the latter is the more primitive.

It is nevertheless a fact that, with a few exceptions, the markings, however variable they may be, are reducible to certain fundamental patterns to which the innumerable variations may be traced back, and their derivation followed and scientifically explained. Let us consider, for instance, another species of Coluber, highly variable in its markings: C. leopardinus, of which the typical form, so called from having been the first described and named, is not by any means to be regarded as the most primitive.

First, we must take for granted that the markings of all such snakes, whether consisting of spots, stripes, or bars, start from a regular arrangement, which may be theoretically represented by four paired longitudinal series on the head and body: (1) Dorsal series (D); (2) Dorso-lateral (DL); (3) Lateral (L); (4) Ventro-lateral (VL). The first starts from the middle line of the head, and is continued along the spine; the second occupies the space between the first and third, which originates at the tip of the snout, passes through the eye, and is continued on the temple and along the side of the body; the fourth follows the lower lip, and extends along each side of the belly. Bearing this in mind, we find that the variety of C. leopardinus named schwoederi, with a vertebral series of paired spots, is to be regarded as the most primitive, from which we can derive, on the one hand, the true leopardinus by imagining a transverse fusion of the spots of series D into a single row, some of the spots often actually revealing, in their biscuit shape, their dual origin; whilst, on the other hand, confluence of the paired spots of the same series into two longitudinal stripes produces the variety named quadrilineatus (see [Plate VII].). In this particular instance, the paired series D has fused into a single streak on the head, and the series L appears to have departed from its primitive course to extend on the upper surface of the head, both in front of and behind the eye.

Many snakes show an interocular band extending from lip to lip, through the eyes, across the interorbital region. In others the lateral stripe L may bifurcate in front of the eye, an upper branch extending across the snout, through transverse fusion of series D and DL, and it may also bifurcate in like manner on the temporal region, fusing with the corresponding marking on the other side to form a W-shaped figure. The pattern of markings on the upper surface of the head is, however, often very complicated, and hence difficult of explanation.

As a second example of the derivation of patterns, we may mention Vipera aspis, which varies enormously as to its mid-dorsal markings, forming, in different individuals or even on different parts of the body, single or paired spots, a zigzag band, or transverse bars; all these are derived from the paired spots of series D. Each pair of spots may fuse and form transversely oval or elliptical spots or bars, or the spots may assume an alternate disposition from which, through confluence, the zigzag or sinuous band results. Thus, spotted and striped patterns may be traced to a common origin, however fundamental the difference between them appears at first sight. If the elements of the four series, D, DL, L, and VL, unite transversely with each other, and also with the spots on the ventral surface, we obtain ringed forms such as the Coral-snakes. That the black nuchal collar of our common Grass-snake is actually formed by the fusion of the spots of three originally distinct series has been proved by tracing the development of the markings in the embryo.

In various species a pair of light streaks extends along the back, bordering the D area, without interfering with the other markings, as we see, among European snakes, in some specimens of Tropidonotus natrix and viperinus, and Vipera berus.

Although it sometimes happens that a definite system of markings prevails throughout a genus, such as the annulate form in the South American Elaps, this is far from being universally the case; many closely allied species, or individuals of the same species, may be distinguished by very different patterns. Even on the same individual we may find two opposite types of markings without any transition, as in two Central American species of widely different genera, Polyodontophis annulatus and Zamenis mexicanus, in which the anterior part of the body is annulate or barred, and the rest longitudinally striped.

It is also a remarkable fact that very often the two sides of the body are not alike in their markings, appearing as if formed of the union, on the median line, of the right and left halves of two individuals. Thus it may happen, in annulate forms, that some of the annuli are broken exactly in the mid-dorsal and mid-ventral lines, and that the halves do not correspond in number on the two sides. In the handsome South American Lachesis alternatus, which derives its specific name from the two series of large C-shaped, dark, light-edged markings which adorn its back, these markings are not always alternating, as is the rule; but some may lie opposite to each other and back to back, this being due to the fact that the numbers of the markings do not correspond on the two sides. In one specimen I count twenty-four of these markings on the left side, and twenty-seven on the right. This shows that great importance cannot be attached to the number of the markings, for systematic purposes. In fact, in some Coral-snakes, Elaps fulvius for instance, the number of annuli may vary from twelve to fifty-two, with every gradation between the extremes. The bilateral asymmetry to which we have alluded produces the chess-board arrangement of the ventral spots in many snakes.

Among the markings which call for investigation as to their meaning, we must allude to the presence, in some Colubrids, of a small, light, dark-edged spot, or of a pair of light dots close together, in the middle of the parietal shields or on each side of the suture between these shields, which correspond in their position to the parietal organ of many Lizards. May not this marking be in some way correlated with sensory organs, like the apical pits on the scales of the body? And what is the explanation of such bizarre signs as the spectacle or the eye-spot on the hood of the Indian Cobra? At present it is as inexplicable as the lugubrious emblem on the thorax of the Death’s-head Moth. It cannot be suggested that it is a warning mark intended to terrify intruders, for when the Cobra is at rest the hood is folded, and the characteristic marking is not displayed; whilst as soon as it is aroused, and the hood expanded, it faces its enemy in such a way that the spectacle, or ocellus, is not to be seen.

First among the most brilliantly coloured snakes, of which there are many, stand the Coral-snakes, Elaps, of America, mostly annulate with red, yellow or white, and black. This striking coloration obtains also in diverse harmless snakes inhabiting the same part of the world, and this coincidence has been adduced in favour of the theory of mimicry, correlated with that of natural selection, which accounts for the resemblance as being of advantage to a harmless species, which is thus mistaken for one notorious for its deadly poison, and advertised as such by its brilliant colours (warning coloration). But other poisonous and much more dangerous snakes are not, as a rule, endowed with brilliant colours. It is true that these also may have their mimics: the Krait, Bungarus cæruleus, and Lycodon aulicus, in India, the Pit-viper, Ancistrodon himalayanus, and Psammodynastes pulverulentus, in the Himalayas and Assam, are good examples of such cases. On the other hand, there are equally striking instances of what one would regard as mimics if they only occurred together; thus, there is no better case of general resemblance between a poisonous and a harmless snake than we find in the Indian Cobra and the Coluber corais of tropical America, where Cobras are absent, or between a Viper and the Boid Enygrus asper, from New Guinea, where no Vipers exist.

Without attempting to offer any suggestion to account for the similarity of markings which prevails in certain parts of the world, attention may be drawn to the predominance of longitudinal dark and light stripes in the Indo-Malayan representatives of the American Elaps, shared by many innocuous snakes of similar form inhabiting the same region, and to the striped tails common to various Colubrids of Madagascar, as if the snakes of a district had agreed to conform to certain fashions in dress.

It is further noteworthy, in relation to the theory of warning coloration, that many Uropeltids, innocent burrowing creatures living underground or concealed under stones or rotting tree-trunks in the forests of Southern India and Ceylon, hardly ever showing themselves in daylight, are among the most striking for their bright yellow or red and black markings. We may point out at the same time the very marked resemblance in form and coloration between the Uropeltid Melanophidium bilineatum, and the Apodal Batrachian Ichthyophis glutinosus, both occurring together in Southern India.

The colour of snakes often harmonizes with their surroundings. Thus, many Tree-snakes, Boid, Colubrid, or Viperid, are of a bright green, like the foliage in which they are concealed. On the other hand, other Tree-snakes are not green, or only some specimens are green, as in the genera Dendraspis and Dispholidus. Desert-snakes are of the yellowish or reddish colour of the sand or rock on which they live, and in species whose range extends over different districts the desert individuals are paler, without or with less distinct markings, as compared to their fellows among other surroundings. In addition to their markings, some snakes are adorned with a metallic iridescent gloss, due to a fine striation of the scales.

The iris is often metallic, gold, bronze, or copper-red, and the black streaks of the head sometimes extend over it.

Although, unlike many lizards, snakes are unable to rapidly alter their colours, some produce a semblance of this phenomenon when inflating their neck or body; this is due to the presence of dark and light markings or of a bright pigment in the interstitial skin, which is not seen when the scales overlap. Thus, in the Indian Tree-snake Dryophis mycterizans the skin between the green or brown scales in the anterior part of the body is black and white, producing a striped pattern when the neck is inflated; the skin of the same region is bright vermilion in the Malay Tropidonotus subminiatus; many more examples could be quoted. The spectacle marking on the hood of the Indian Cobra involves the scales as well as the interstitial skin.

As a rule there are no sexual differences in colour. Yet these are so marked in our Common Adder that the sex of a specimen can nearly always be recognized by the coloration. This is, however, the exception, even in the genus to which the Adder belongs. A nuptial dress is unknown in snakes.

A special livery for the young is rather exceptional, but very often the new-born is more vividly coloured than its parents, and in many black varieties the young is similar to the typical form. Some green Tree-Boids (Chondropython and Corallus caninus) are not green, but yellowish, cream-colour, or pinkish, when young, the green appearing around the white spots, which are the remains of the ground colour, and gradually spreading over the whole body. Conversely, the young of a variety of the Pit-viper Lachesis wagleri, common in the Malay Peninsula, is green, and the adult black and yellow. In the young of Grayia ornata, a West African Water-snake, the markings of the young are to those of the adult like positive and negative in photography, the white bars, forked on the sides, which extend across the black back of the former being gradually transformed into black bars on a light ground in the latter; in such a case it is impossible to decide whether the dark or the light parts are to be considered as the ground colour.

That the skin of many snakes contains soluble colouring matter of a special kind is well known, green snakes, such as Dryophis prasinus and Lachesis gramineus staining the spirit in which they are preserved. Chemists have not yet paid attention to this question, which requires investigation.

Melanism is frequent in snakes, and sometimes affects all individuals in the same locality. It seems undesirable to bestow varietal names on such aberrations, as is so frequently done by systematists, any more than we should in the case of albinos. Melanism may be produced in two ways: by an extension of the black markings, which invade the whole surface, as in the males of Vipera berus; or by a general darkening of the ground colour and of the markings, as in the females of the same species. In the latter case, the markings reappear under certain lights or after a prolonged sojourn in spirits. Sometimes, as in Zamenis gemonensis, the uniform black colour appears only as the snake approaches the adult condition, the young having the normal livery.

Partial albinism is rare; perfect albinism, characterized by absence of black pigment in the eye, rarer still. Cases have been observed, among European species, in Tropidonotus natrix and tessellatus, in Coluber longissimus, and in Coronella austriaca.

CHAPTER IV
SKELETON

The typical Ophidian skull is characterized by a solidly ossified brain-case, with the distinct frontals and the united parietals extending downwards to the basisphenoid, which is large and produced forward into a rostrum extending to the ethmoidal region. The nasal region is less completely ossified, and the paired nasals are often attached only at their base. The occipital condyle is either trilobate and formed by the basioccipital and the exoccipitals, or a simple knob formed by the basioccipital; the supraoccipital is excluded from the foramen magnum. The basioccipital may bear a strong, curved ventral process or hypapophysis (in the Vipers).

The prefrontal is situated, on each side, between the frontal and the maxillary, and may or may not be in contact with the nasal; the postfrontal, usually present, borders the orbit behind, rarely also above, and in the Pythons a supraorbital is intercalated between it and the prefrontal.

Fig. 3—Skull of Python amethystinus. (From British Museum Catalogue of Snakes)

an, Angular; ar, articular; bo, basioccipital; bs, basisphenoid; cor, coronoid; c.a, columella auris (stapes); d, dentary; eo, exoccipital; epg, ectopterygoid (transverse); f, frontal; m, maxillary; n, nasal; p, parietal; pl, palatine; pm, premaxillary; prf, prefrontal; pro, proötic; pg, pterygoid; ptf, postfrontal; q, quadrate; so, supraoccipital; sor, supraorbital; sp, splenial; ste, supratemporal; tu, turbinal; v, vomer.

The premaxillary is single and small, and as a rule connected with the maxillary only by ligament. The paired vomer is narrow. The palatine and pterygoid are elongate and parallel to the axis of the skull, the latter diverging behind and extending to the quadrate or to the articular extremity of the mandible; the pterygoid is connected with the maxillary by the ectopterygoid or transverse bone, which may be very elongate, and the maxillary often emits a process towards the palatine, the latter bone being usually produced inwards and upwards towards the anterior extremity of the basisphenoid. The quadrate is usually large and elongate, and attached to the cranium through the supratemporal (often regarded as the squamosal). In rare cases (Miodon, Polemon) the transverse bone is forked, and articulates with two branches of the maxilla. The quadrate and the maxillary and palatopterygoid arches are more or less movable to allow for the distension required by the passage of prey, often much exceeding the calibre of the mouth. For the same reason, the rami of the lower jaw, which consist of dentary, splenial, angular, and articular elements, with the addition of a coronoid in the Boidæ and a few other small families, are connected at the symphysis by a very extensible elastic ligament.

The hyoid apparatus is reduced to a pair of cartilaginous filaments situated below the trachea, and united in front.

There are various modifications according to the genera. A large vacuity may be present between the frontal bones and the basisphenoid (Psammophis, Cœlopeltis); the maxillary may be much abbreviated and movable vertically, as in the Viperidæ; the pterygoids may taper and converge posteriorly, without any connexion with the quadrate, as in the Amblycephalidæ; the supratemporal may be much reduced, and wedged in between the adjacent bones of the cranium; the quadrate may be short or extremely large; the prefrontals may join in a median suture in front of the frontals; the dentary may be freely movable, and detached from the articular posteriorly.

Fig. 4—Skull of Typhlops lumbricalis. (From British Museum Catalogue of Snakes)

Lettering of the bones as in Fig. [3]

Fig. 5—Skull of Glauconia macrolepis. (From British Museum Catalogue of Snakes)

Lettering of the bones as in Fig. [3]

The deviation from the normal type is much greater still when we consider the degraded, worm-like members of the families Typhlopidæ (Fig. [4], p. [43]) and Glauconiidæ (Fig. [5]), in which the skull is very compact and the maxillary much reduced. In the former this bone is loosely attached to the lower aspect of the cranium; in the latter it borders the mouth, and is suturally joined to the premaxillary and the prefrontal. In both the tranverse bone and the supratemporal are absent, but the coronoid element is present in the mandible.

Fig. 6—Skull of Tropidonotus natrix. (From British Museum Catalogue of Snakes)

Lettering of the bones as in Fig. [3]

The principal modifications of the skull in the European genera may be contrasted as in the following synopsis:

I. Quadrate articulating with the cranium, supratemporal absent; mandible much shorter than the skull, with coronoid bone; maxillary small, on lower aspect of cranium; pterygoids not extending to quadrate; nasals forming long sutures with the premaxillary, prefrontals, and frontal

Typhlops.

II. Quadrate suspended from the supratemporal; mandible at least as long as the skull; pterygoids extending to quadrate or mandible.

A. Mandible with coronoid bone; nasals in sutural contact with frontals and prefrontals; transverse bone short, not projecting much beyond cranium; maxillary not half as long as mandible, which is not longer than skull (to occiput)

Eryx.

Fig. 7—Skull of Zamenis gemonensis. (From British Museum Catalogue of Snakes)

B. No coronoid bone; nasals isolated.

1. Maxillary elongate, not movable vertically.

a. Maxillary half as long as mandible.

Supratemporal half as long as skull, projecting far beyond cranium; mandible much longer than skull

Tropidonotus.

Supratemporal not half as long as skull, projecting far beyond cranium; mandible much longer than skull

Zamenis.

Fig. 8—Skull of Coluber longissimus. (From British Museum Catalogue of Snakes)

Supratemporal not half as long as skull, projecting but slightly beyond cranium; mandible much longer than skull

Coluber.

Supratemporal not half as long as skull, not projecting beyond cranium; mandible not longer than skull

Coronella, Contia.

b. Maxillary not half as long as mandible, which is longer than skull; supratemporal not half as long as skull, projecting beyond cranium.

Fig. 9—Skull of Coronella austriaca. (From British Museum Catalogue of Snakes)

Quadrate longer than supratemporal; maxillary much longer than quadrate, nearly straight in front of prefrontal; a large vacuity between the frontal bones and the basisphenoid

Cœlopeltis.

Quadrate not longer than supratemporal; maxillary little longer than quadrate, strongly curved in front of prefrontal

Macroprotodon.

Quadrate longer than supratemporal; maxillary little longer than quadrate, nearly straight in front of prefrontal

Tarbophis.

Fig. 10—Skull of Vipera lebetina. (From British Museum Catalogue of Snakes)

Lettering of the bones as in Fig. [3]

2. Maxillary much abbreviated and erectile; supratemporal not half as long as skull; mandible much longer than skull; basioccipital with a strong process.

Maxillary bone solid

Vipera.

Maxillary bone hollowed out

Ancistrodon.

The vertebræ number 130 to 500—in the European forms 147 (Vipera ursinii) to 330 (Coluber leopardinus).

The vertebral column consists of an atlas (composed of two vertebræ) without ribs; numerous precaudal vertebræ, all of which, except the first or first three, bear long, movable, curved ribs with a small posterior tubercle at the base, the last of these ribs sometimes forked; two to ten so-called “lumbar vertebræ” without ribs, but with bifurcate transverse processes (lymphapophyses) enclosing the lymphatic vessels; and a number of ribless caudal vertebræ with simple transverse processes. When bifid, the ribs or transverse processes have the branches regularly superposed.

The centra have the usual cup-and-ball articulation, with the nearly hemispherical or transversely elliptic condyle at the back (procœlous vertebræ), whilst the neural arch is provided with additional articular surfaces in the form of pre- and post-zygapophyses, broad, flattened, and overlapping, and of a pair of anterior wedge-shaped processes called zygosphene, fitting into a pair of corresponding concavities, zygantrum, just below the base of the neural spine. Thus the vertebræ of snakes articulate with each other by eight joints in addition to the cup-and-ball on the centrum, and interlock by parts reciprocally receiving and entering one another, like the joints called “tenon-and-mortice” in carpentry. The precaudal vertebræ have a more or less high neural spine which, as a rare exception (Xenopholis), may be expanded and plate-like above, and short or moderately long transverse processes to which the ribs are attached by a single facet. The centra of the anterior vertebræ emit more or less developed descending processes, or hæmapophyses, which are sometimes continued throughout (Fig. [11], A), as in Tropidonotus, Vipera, and Ancistrodon, among European genera.

Fig. 11—Posterior Precaudal Vertebræ of Lioheterodon (A) AND Heterodon (B). (From British Museum Catalogue of Snakes)

a, Back view; b, lower view; c, side view.

In the caudal region, elongate transverse processes take the place of ribs, and the hæmapophyses are paired, one on each side of the hæmal canal. In the Rattlesnakes the seven or eight last vertebræ are enlarged and fused into one.

No snake shows any rudiments of the pectoral arch, but remains of the pelvic are found in the Typhlopidæ, the Glauconiidæ, the Boidæ, and the Ilysiidæ. In the first these vestiges are reduced to a single bone (ilium?) on each side; in the second they consist of ilium, pubis, and ischium, the latter forming a ventral symphysis, and a rudimentary femur; whilst in the third there is a long ilium, attached to the lower branch of the first bifurcate transverse process of the lumbar vertebræ, bearing three short bones, the longest of which, regarded as the femur, terminates in a claw-like spur which, in males at least, usually appears externally on each side of the vent.

CHAPTER V
DENTITION

In the most generalized snakes—those which show the nearest approach to lizards—teeth are present not only on the rami of both jaws, but also on the premaxillary bone, on the palatines, and on the pterygoids. A reduction of the dentition takes place in various genera, in which the teeth of either the upper or the lower jaw, and of the palatines or pterygoids, or both, may be absent, and the premaxillary is devoid of teeth in the great majority, including all European representatives, of the Ophidia.

In the egg-eating snakes of the genera Dasypeltis and Elachistodon the dentition is very much reduced, in accordance with the peculiar régime, and this deficiency is compensated by the development on some of the anterior thoracic vertebræ of long, tooth-like processes (hypapophyses) directed forwards, and capped with a remarkably dense, vitreous tissue simulating enamel, the function of these tooth-like processes being to break the shell of the egg within the gullet, where none of its contents are lost, the shell being afterwards rejected through the mouth in the form of a pellet.

With the exception of the worm-like Typhlopidæ, which are provided with a few teeth in the upper jaw only, European snakes have teeth on the maxillary, palatine, pterygoid, and dentary bones. Unless the maxillary be strongly abbreviated and modified in connexion with the poison apparatus, as in the Viperidæ, the teeth in the jaws as well as on the palate form single longitudinal series; they are elongate, conical, with or without a sharp posterior edge, more or less recurved, acutely pointed, sometimes needle-like, and directed backwards, as behoves their function, which, in addition to attack and defence, is to prevent the retrogression of the prey in the act of prehension and deglutition. A notable exception occurs in the genus Iguanognathus, from Sumatra, all the teeth having spatulate crowns ribbed along the outer side. Unfortunately, nothing is known as to the food of this remarkable snake. The teeth are coated with a thin layer of enamel. It was held, for a time, that the glossy outer coating was only due to a denser structure of the dentine. As in all living Reptiles with the exception of the Crocodiles, the teeth are not implanted in true sockets, but simply ankylosed to the bone on which, when detached, their slightly enlarged base, or rather the bony tissue on which it rests, leaves a shallow impression, or pseudo-socket. In the process of biting or feeding, some of the teeth are frequently lost, and are readily replaced by others lying in reserve in the gum at the inner side, and becoming fixed to the bone soon after a vacancy occurs. Such replacement teeth, of different grades of development, form several series, so that in a snake like our common Tropidonotus the mouth may contain four times as many teeth as are functional, without reckoning different earlier stages of tooth germs which escape ordinary observation, being placed vertically one above the other.

Three types of teeth, connected by every intermediate step, are distinguished: the solid, the grooved, and the canaliculated or tubular, so-called “perforated”; the third, as we shall explain, being only a further modification of the second. In the grooved tooth, a sulcus runs along the anterior or outer surface, its object being to convey into the wound the secretion of a poison gland. It varies in depth according to the species, and may be so slight as to escape detection without a very strong magnifying glass. In some the sulcus may be very deep and wide, forming a canal round which the tooth folds to the extent of its borders nearly meeting; from this condition the so-called “perforated” fang is derived through the complete fusion of the borders of the tooth, and the obliteration of the line of union except at each extremity. The structure of such a fang may be best understood by imagining a tooth, lined all round with the same layer of dentine and enamel, being flattened out in a vertical plane and then folded over, the outer edges coalescing on the front median line in such a way that the inner wall of the tooth is in reality the anterior surface, and the outer wall the posterior surface, of the ordinary tooth.

Grooved teeth, with open canal, are situated either at the anterior extremity (Proteroglyphs) or at the posterior extremity (Opisthoglyphs) of the maxillary bone, usually followed or preceded by a series of solid teeth, which in some cases may likewise show a more or less distinct groove. Such may also be present on the teeth of the lower jaw, as in the European Cœlopeltis, in some specimens of which a faint groove is visible on the outer side with the aid of a strong lens.

The tubular fangs of the Viperidæ are inserted on the posterior extremity of the much abbreviated and erectile maxillary bone, which bears no other teeth. The Proteroglyphs (Cobras, Coral-snakes, Sea-snakes) and the Solenoglyphs (Vipers, Pit-vipers, Rattlesnakes) may be regarded as the diverging extremes in the development of the poison apparatus, both culminating in forms with tubular fangs, the former as derived directly from the Aglyphs (harmless snakes), the latter from the Opisthoglyphs, likewise evolved out of the Aglyphs. That the insertion of the poison fangs of the Viperidæ is really on the posterior extremity of the maxillary bone is evident from the condition of the bone in its recumbent position, especially in the African Viper, Causus, which in several respects departs less markedly from the Colubrid type than our European Vipers.

The poison fangs of the Viperidæ appear to be movable, folding in the mouth when at rest, and erected, or even thrust forward, when ready to act. This, however, is simply due to the mobility of the maxillary bone, to which they are ankylosed as in all other snakes. There are normally two equally-developed fangs, close together and side by side, to each maxillary, followed by several replacement fangs loosely attached behind them, usually in two series of four. When the two fangs are in situ, they of course both function in the act of biting, although only one is in relation with the single poison duct; often, however, there is only one fang in position, either the right or the left, the place of the other being indicated by a shallow socket which will soon be filled by one of the posterior reserve fangs moving forward and becoming ankylosed to the bone. Snake-charmers who extract the poison fangs of the snakes they use for their performances have therefore to renew the operation frequently, unless they amputate the bone on which the fangs are inserted, an injury which the creature does not long survive.

The dentition of the snakes in which the maxillary bone is not movable vertically falls under three divisions: the Aglyphs, in which the teeth are all solid; the Opisthoglyphs, in which one or more (usually two) of the hindermost teeth are provided with a groove; and the Proteroglyphs, in which grooved or canaliculated teeth are situated in front, followed or not by solid teeth. Beyond these three principal divisions, the dentition furnishes important characters for the classification, although that importance has sometimes been over-estimated. The maxillary teeth may be equal in length (Isodonts), or the anterior the longer (Lycodonts), or the posterior the longer, increasing gradually in size (Coryphodonts) or abruptly, without (Syncranterians) or with a diastema, or break, in front of them (Diacranterians). These categories are, however, so completely connected as to preclude their use in taxonomy beyond helping to define genera. The number of maxillary teeth and the relative proportions and disposition of the mandibular teeth also afford useful generic characters.

The European genera may be arranged as follows, according to the dentition:

I. Teeth few, disposed in a transverse series in the upper jaw only

Typhlops.

II. Teeth in both jaws and on the palatines and pterygoids.

A. A series of solid teeth along the maxillary; no grooved teeth.

1. Anterior maxillary and mandibular teeth longest; 9 or 10 maxillary teeth

Eryx.

2. Maxillary teeth equal, or increasing in size posteriorly.

a. Mandibular teeth 17 to 30; maxillary teeth 15 to 22.

Posterior maxillary teeth longest; mandibular teeth subequal, more than 20

Tropidonotus.

Posterior maxillary teeth longest; mandibular teeth not more than 20, posterior smallest

Zamenis.

Maxillary teeth subequal; mandibular teeth 20 to 25, posterior smallest

Coluber.

b. Mandibular teeth 14 or 15, subequal; maxillary teeth 12 to 15.

Maxillary teeth increasing in size

Coronella.

Maxillary teeth subequal

Contia.

B. One or two enlarged grooved fangs behind the series of solid maxillary teeth.

14 to 17 subequal solid maxillary teeth, forming a continuous series; 21 to 23 mandibular teeth, anterior strongly enlarged

Cœlopeltis.

9 to 11 solid maxillary teeth, fourth and fifth or fifth and sixth enlarged, followed by an interspace; sixth mandibular tooth fang-like, followed by an interspace

Macroprotodon.

9 or 10 solid maxillary teeth, forming a continuous series, decreasing in length posteriorly; anterior mandibular teeth strongly enlarged

Tarbophis.

C. Maxillary with only two large canaliculated fangs side by side, one of which may be missing; anterior mandibular teeth longest

Vipera, Ancistrodon.

Fig. 12—Maxillary and Mandible of—(a) Tarbophis fallax; (b) Cœlopeltis monspessulana; (c) Macroprotodon cucullatus. (From British Museum Catalogue of Snakes)

In counting the teeth for the purpose of using this key, care must be taken to ascertain the full number, as it frequently happens that one or more are missing; but their place is indicated by the shallow pits in which their base was implanted, the overlooking of which might convey the impression of a hiatus such as is characteristic of certain genera—Macroprotodon, for instance. Needless to say, the loose teeth which are in reserve on the inner side of the jaws or behind the tubular fangs are not taken into consideration, the numbers given being those of functional teeth only. Although as a rule the teeth can be counted easily, on a specimen preserved in spirit, by simply pushing aside the lips and gums with the finger, it is sometimes necessary to remove and clean the bones of the jaws, an operation which does not require much skill.

CHAPTER VI
POISON APPARATUS—DIFFERENT KINDS OF POISONS

The gland which secretes the poison is a modification of the parotid salivary gland of other Vertebrates, and is usually situated on each side of the head below and behind the eye, invested in a muscular sheath. It is provided with large alveoli in which the venom is stored before being conveyed by a duct to the base of the channelled or tubular fang through which it is ejected.

In the Vipers, which furnish examples of the most highly developed poison apparatus, although inferior to some in its toxic effects, the poison gland is very large and in intimate relation with the masseter or temporal muscle, consisting of two bands, the superior arising from behind the eye, the inferior extending from the gland to the mandible. When the snake bites, the jaws close up, causing the gland to be powerfully wrung, and the poison pressed out into the duct. From the anterior extremity of the gland the duct passes, below the eye and above the maxillary bone, where it makes a bend, to the basal orifice of the poison fang, described above (p. [55]), which is ensheathed in a thick fold of mucous membrane, the vagina dentis. By means of the movable maxillary bone (supra, p. [49]) hinged to the prefrontal, and connected with the tranverse bone which is pushed forward by muscles set in action by the opening of the mouth, the tubular fang is erected and the poison discharged through the distal orifice in which it terminates.

Fig. 13—Poison Apparatus of Rattlesnake: Venom Gland and Muscles (Lateral View). (After Duvernoy)

a, Venom gland; a´, venom duct; b, anterior temporal muscle; b´, mandibular portion of same; c, posterior temporal muscle; d, digastricus muscle; e, posterior ligament of gland; f, sheath of fang; g, middle temporal muscle; h, external pterygoid muscle; i, maxillary salivary gland; j, mandibulary salivary gland.

In some of the Proteroglyphous Colubrids, as we have seen, the poison fangs are not tubular, but only channelled and open along the anterior surface; and as the maxillary bone in these snakes is more or less elongate, and not or but slightly movable vertically, the poison duct runs above the latter, making a bend only at its anterior extremity, and the tranverse bone has not the same action on the erection of the fangs. Otherwise the mechanism is the same.

In the Opisthoglyphous Colubrids, with grooved teeth situated at the posterior extremity of the maxilla, a small posterior portion of the upper labial or salivary gland is converted into a poison-secreting organ, distinguished by a light yellow colour, provided with a duct larger than any of those of the labial gland, and proceeding inward and downward to the base of the grooved fang; the duct is not in direct connexion with the groove, but the two communicate through the mediation of the cavity enclosed by the folds of mucous membrane surrounding the tooth, and united in front.

The reserve or successional teeth, which are always present just behind or on the side of the functional fang of all venomous snakes, are in no way connected with the duct until called upon to replace a fang that has been lost. It could not be otherwise, since the duct would require a new terminal portion for each new fang; and as the replacement takes place alternately from two parallel series, the new poison-conveying tooth does not occupy exactly the same position as its predecessor.

Two genera, Doliophis among the Elapine Colubrids, and Causus among the Viperids, are highly remarkable for having the poison gland and its duct of a great length, extending along each side of the body and terminating in front of the heart. Instead of the muscles of the temporal region serving to press out the poison into the duct, this action is performed by those of the side of the body.

When biting, a Viperid snake merely strikes, discharging the venom the moment the fangs penetrate the skin, and then immediately leaves go. A Proteroglyph or Opisthoglyph, on the contrary, closes its jaws like a dog on the part bitten, often holding on firmly for a considerable time.

The poison, which is mostly a clear limpid fluid of a pale straw or amber colour, more rarely greenish, sometimes with a certain amount of suspended matter, is exhausted after several bites, and the glands have to recuperate.

It must be added that the poison can be ejected otherwise than by a bite, as in the so-called Spitting Snakes of the genera Naia and Sepedon. The fact that some of these deadly snakes when irritated are in the habit of shooting poison from the mouth, at a distance of 4 to 8 feet, even apparently aiming at a man’s face, has been too often witnessed in India and Malaya, and especially in Africa, from the days of the ancient Egyptians, for any doubt to subsist as to their being endowed with this faculty, but the mechanism by which this action is produced has not been satisfactorily explained. In all probability, the poison escapes from the sheath of mucous membrane surrounding the base of the fangs, and is mixed with ordinary saliva, the membranes of the mouth perhaps acting as lips, in which case the term “spitting” would not be incorrect. The spitting, which may take place three or four times in succession, has been observed to be preceded by some chewing movements of the jaws. If reaching the eye, the poisonous fluid causes severe inflammation of the cornea and conjunctiva, but no more serious results if washed away at once.

Snake poisons is a subject which has always attracted much attention, and which has made great progress within the last quarter of a century, especially as regards the defensive reaction by which the blood may be rendered proof against their effect by processes similar to vaccination—antipoisonous serotherapy. The studies to which we allude have not only conduced to a method of treatment against snake-bites, but have thrown a new light on the great problem of immunity. They have shown that the antitoxic serums do not act as chemical antidotes in destroying the venom, but as physiological antidotes; that, in addition to the poison glands, snakes possess other glands supplying their blood with substances antagonistic to the poison, such as also exist in various animals refractory to snake poison, the hedgehog and the mungoose for instance. Unfortunately, the specificity of the different snake poisons is such that, even when the physiological action appears identical, serum injections or graduated direct inoculations confer immunity towards one species or a few allied species only. Thus, a European in Australia who had become immune to the poison of the deadly Notechis scutatus, manipulating these snakes with impunity, and was under the impression that his immunity extended also to other species, when bitten by a Denisonia superba, an allied Elapine, died the following day. In India, the serum prepared with the venom of Naia tripudians has been found to be without effect on the poison of Naia bungarus, the two species of Bungarus, and the Vipers Vipera russelli, Echis carinatus, and Lachesis gramineus. Vipera russelli serum is without effect on Colubrine venoms, and on those of Echis and Lachesis. In Brazil, serum prepared with the venom of Lachesis lanceolatus has proved to be without action on Crotalus poison. These examples, and others which could be given, show that the hopes which were at first entertained as to the benefits to be conferred on mankind by the serum treatment were somewhat over-sanguine—at least as regards countries like India, where, different kinds of poisonous snakes occurring together, it is sometimes impossible to know by which the bite has been inflicted.

Chemistry teaches that snake venoms consist for the most part of solutions of modified proteids, and all attempts to separate the toxic principles from such proteids have hitherto been unsuccessful. Accordingly, at the present time we must regard such toxic principles as residing in some special grouping of a portion of the atoms in the complex venom proteid molecule. The analysis of their physiological actions has proved them to be made up of a great many more constituents than would be imagined from their chemical composition.

The effect of the poison of Proteroglyphous Colubrids (Hydrophids, Cobras, Bungarus, Elaps, Pseudechis, Notechis, Acanthophis) is mainly on the nervous system, respiratory paralysis being quickly produced by bringing the poison into contact with the central nervous mechanism which controls respiration; the pain and local swelling which follow a bite are not usually severe.

Viper poison (Vipera, Echis, Lachesis, Crotalus) acts more on the vascular system, bringing about coagulation of the blood and clotting of the pulmonary arteries; its action on the nervous system is not great, no individual group of nerve cells appears to be picked out, and the effect upon respiration is not so direct; the influence upon the circulation explains the great depression which is a symptom of Viperine poisoning. The pain of the wound is severe, and is speedily followed by swelling and discoloration. The symptoms produced by the bite of the European Vipers are thus described by the best authorities on snake poison (Martin and Lamb): The bite is immediately followed by local pain of a burning character; the limb soon swells and becomes discoloured, and within one to three hours great prostration, accompanied by vomiting, and often diarrhœa, sets in. Cold, clammy perspiration is usual. The pulse becomes extremely feeble, and slight dyspnœa and restlessness may be seen. In severe cases, which occur mostly in children, the pulse may become imperceptible and the extremities cold; the patient may pass into coma. In from twelve to twenty-four hours these severe constitutional symptoms usually pass off; but in the meantime the swelling and discoloration have spread enormously. The limb becomes phlegmonous, and occasionally suppurates. Within a few days recovery usually occurs somewhat suddenly, but death may result from the severe depression or from the secondary effects of suppuration. That cases of death, in adults as well as in children, are not infrequent in some parts of the Continent is mentioned in the last chapter of this Introduction.

The bite of all the Proteroglyphous Colubrids, even of the smallest and gentlest, such as the Elaps or Coral-snakes, is, so far as known, deadly to man. The Viperidæ differ much among themselves in the toxicity of their venom. Some, such as the Indian Vipera russelli and Echis carinatus, the American Ancistrodon, Crotalus, Lachesis mutus and lanceolatus, the African Causus, Bitis, and Cerastes, cause fatal results unless a remedy be speedily applied. On the other hand, the Indian and Malay Lachesis seldom cause the death of man, their bite in some instances being no worse than the sting of a hornet. The bite of the larger European Vipers may be very dangerous, and followed by fatal results, especially in children, at least in the hotter parts of the Continent; whilst the small Vipera ursinii, which hardly ever bites unless roughly handled, does not seem to be possessed of a very virulent poison, and, although very common in some parts of Austria-Hungary, is not known to have ever caused a serious accident.

It is noteworthy that the size of the poison fangs is in no relation to the virulence of the venom. The comparatively innocent Indo-Malay Lachesis alluded to above have enormous fangs, whilst the smallest fangs are found in the most justly dreaded of all snakes, the Hydrophids.

Little is known of the physiology of the poison of the Opisthoglyphous Colubrids, except that in most cases it approximates to that of the Proteroglyphs. Experiments on Cœlopeltis, Psammophis, Trimerorhinus, Dipsadomorphus, Trimorphodon, Dryophis, Tarbophis, Hypsirhina, and Cerberus, have shown these snakes to be possessed of a specific poison, small mammals, lizards, or fish, being rapidly paralyzed and succumbing in a very short time, whilst others (Eteirodipsas, Ithycyphus) do not seem to be appreciably venomous. Man, it is true, is not easily affected by the bite of these snakes, since, at least in most of those which have a long maxillary bone, the grooved fangs are placed too far back to inflict a wound under ordinary circumstances. There are, however, exceptions. A case was reported a few years ago of a man in South Africa nearly dying as a result of the bite of the Boomslang, Dispholidus typus, the symptoms, carefully recorded, being those characteristic of Viperine poisoning, an important fact to oppose to the conclusions, based on the physiological experiments on Cœlopeltis, which appeared to disprove the theory that the Viperidæ may have been derived from Opisthoglyphous Colubrids.

Experiments made with the secretion of the parotid gland of Tropidonotus and Zamenis have shown that even Aglyphous snakes are not entirely devoid of venom, and point to the conclusion that the physiological difference between so-called harmless and poisonous snakes is only one of degree, just as there are various steps in the transformation of an ordinary parotid gland into a poison gland or of a solid tooth into a tubular fang.

The question whether all snakes are immune to their own poison is not yet definitely settled. Most snakes certainly are, and it is a remarkable fact that certain harmless species, such as the North American Coronella getula and the Brazilian Rhachidelus brazili, are proof against the poison of the Crotalines which frequent the same districts, and which they are able to overpower and feed upon. The Cribo, Spilotes variabilis, is the enemy of the Fer-de-lance in St. Lucia, and it is said that in their encounters the Cribo is invariably the victor. Repeated experiments have shown our Common Snake, Tropidonotus natrix, not to be affected by the bite of Vipera berus and V. aspis, this being due to the presence, in the blood of the harmless snake, of toxic principles secreted by the parotid and labial glands, and analogous to those of the venom of these Vipers.

The Hedgehog, the Mungoose, the Secretary Bird, and a few other birds feeding on snakes, are known to be immune to an ordinary dose of snake poison; whether the pig may be considered so is still uncertain, although it is well known that, owing to its subcutaneous layer of fat, it is often bitten with impunity. The Garden Dormouse (Myoxus quercinus) has recently been added to the list of animals refractory to Viper poison.

CHAPTER VII
NERVOUS SYSTEM—SENSE ORGANS

The brain is small and of very oblong shape. It consists of smooth cerebral hemispheres, small optic lobes, a still smaller cerebellum, and long olfactory lobes; the pineal body is not accompanied by a parietal organ. The spinal accessory cranial nerve is absent, and the sympathetic system is but feebly developed.

The eyes have been noticed above (p. [12]). When normally developed they are susceptible of a slight movement under the transparent disc, quite independent from the cornea, which covers them, and from which they are separated by the so-called “lacrymal chamber.” There are two lacrymal glands, one in front and one behind; the lacrymal duct opens into the posterior nares. A sclerotic bony ring is absent.

The olfactory organ proper is little developed, but is accompanied by an accessory organ, Jacobson’s organ, consisting of a pair of pediculate, cup-shaped sacs, between the nasal sacs and the roof of the mouth, encapsuled by the vomers and the turbinal bones, lined by olfactory epithelium, and opening in the mouth just in front of the choanæ. As this organ, richly provided with nerves, communicates with the inside of the mouth, its function may be to smell the prey as it passes through previous to deglutition. Snakes cannot be credited with a keen sense of smell, although undoubtedly guided by it during the nuptial period.

In the more thoroughly aquatic snakes, the nostril may be closed, when respiration is suspended, by a spongy tissue, which acts as a stopper, and such nostrils are called “valvular,” although a valve is not, in the strict sense, present; when the animal breathes, the nostril is opened by a compression, through special muscles, of the cavernous tissue. In some Sand-snakes the narial opening may be reduced to a crescentic slit.

The sense of hearing is not much developed. Tympanum, tympanic cavity, and Eustachian tubes are absent. In the typical snakes a long columellar rod (the stapes), with a fibrous or cartilaginous pad at the outer end, extends from the fenestra ovalis in the cranium to the quadrate, but in the degraded burrowing forms the stapes is a small bony plate closing the fenestra ovalis.

With one exception (Eryx jaculus, which is said by Schreiber to lap like a lizard), the tongue is not used for drinking or for the prehension or gustation of food, nor for hissing, but is a tactile organ protruded on any object the snake wishes to probe. It is slender and deeply bifid at the end, smooth, very protractile, often quite to the length of the head, and furnished with many sensory corpuscules. It is darted and vibrated on the least excitement, and is usually looked upon by the ignorant as a “sting.” In most snakes it is much pigmented, dark brown or black; in a few it is flesh-coloured or bright red. The tongue is entirely retractile into a sheath below the glottis and opening in front of it; it is always withdrawn into the sheath when the snake bites or feeds.

Other organs, which, in the absence of a satisfactory explanation of their use, have been termed “organs of a sixth sense,” reside in the head-shields and scales of many snakes, and in the deep pits on the sides of the head which are characteristic of various Boidæ and a few Colubridæ.

Scales often show, near their posterior extremity, one or two small light spots or impressions, caused by a thinning of the epidermis, which have been called “apical pits”; they appear to coincide with the terminations of nerve fibres extending along the epidermal folds of the skin. Similar organs sometimes form series on the borders of some of the head-shields, this being particularly noticeable in the Typhlopidæ.

The large and deep pit situated between the nostril and the eye (loreal pit) in the Crotaline Viperidæ—whence the name Pit-vipers, or that of “cuatro naricas” which is bestowed on them by the Spaniards of Mexico—is divided into two chambers: an outer with large external orifice, and an inner, rather more posterior in position and occupying an excavation on the outer face of the maxillary bone. The inner walls of these chambers are very thin and membranous, and form a partition separating the two, except for the presence of a minute opening; this partition is stretched across the hollow of the maxillary bone like the membrane of a drum, and is supplied with blood-vessels and nerves, the latter terminating in cells of variable form. The use of the organ, thus situated at the base of the poison fang, and therefore in close proximity to the sphincter of the poison duct, is still unknown.

Several of the Boidæ, such as Python and Corallus, have deep pits in some of the upper and lower labial shields, or also on each side of the rostral shield; these problematic organs are in all probability also sensory.

CHAPTER VIII
VISCERA

In most snakes there is a very marked asymmetry of the viscera and their blood-supply, the organs of the right side being anterior to, as well as larger than, those of the left.

The heart in most cases is situated between the anterior seventh and the anterior fourth of the body; it may be much farther back, beyond the anterior third, in Doliophis, Platurus, and some Viperidæ and Amblycephalidæ, in the middle in Chersydrus. It is of rather elongate form, enclosed in a pericardium in which it lies freely, and has a sinus venosus, two auricles, and a single ventricle divided by a septum. Three arteries leave the ventricle, the pulmonary and two systemic arches. The right systemic arch gives off the carotid artery, which in many snakes, the common Grass-snake for instance, may branch into two, or in others be double from its origin. The anterior abdominal vein is single in most snakes, double in some Boidæ, and conveys blood from the ventral body-wall to the liver. The caudal vein is continued as the renal portal. Veins which have been regarded as remains of the two posterior cardinal of lower Vertebrates have been found in some of the Boidæ.

The bifurcate transverse processes of the vertebræ at the limit between the body and tail enclose the lymph-hearts, which are large and more or less elongate, metamerically divided into several chambers, the right often more developed than the left. The thymus gland lies on each side of the trachea, near the heart, and the thyroid gland is in the middle line, close to the base of the carotid artery.

The trachea is long, and the tracheal rings may be complete in front and incomplete behind, or incomplete throughout. The bronchus opens at once into the more or less elongate, usually single lung, with or without a rudiment of a second, which seems to be constantly the left; in some snakes the lung extends nearly to the cloacal region. In most of the Boidæ there are two well-developed lungs, the left shorter than the right. The lung has highly cellular walls in front, and becomes thin-walled, smooth, or but little vascular, behind, where it may receive its blood from the systemic and not from the pulmonary circulation. In the Typhlopidæ and Viperidæ, as well as in some of the Boidæ, Colubridæ, and Amblycephalidæ, the posterior end or the greater part of the trachea may have its wall enlarged and provided with air cells, resembling the normal lung, with which it is usually continuous; this has been called the “tracheal lung,” but, although serving as an accessory breathing organ, it is not a prolongation of the true lung, nor does it represent the missing left lung, as has been believed by some authors.

The glottis has a longitudinal slit, and can be projected forwards when the pharynx is obstructed by a voluminous prey. An epiglottis is usually absent, or represented by a rudiment. It is, however, present in some large American species of Coluber (Pityophis), said to produce, when hissing, a loud and hoarse sound which has been compared to the bellow of the bull—hence the popular name of Bull-snakes by which they are known. It has also been found in a few allied species from Mexico, for which the genus Epiglottophis has been proposed. This epiglottis is a narrow, thin flap, erect in front of the glottis; it is not hinged, and therefore not capable of falling down to cover the opening of the windpipe during the process of swallowing, its function evidently being to increase the sound produced by the escape of the air from the windpipe.

The larynx is represented by two longitudinal bands of cartilage, united by transverse bands; it is extremely long in some snakes (Leptognathus).

The œsophagus, which may be extremely elongate, sometimes measuring almost one-third of the digestive canal, passes into the tubular or sac-like stomach, often with thickened walls, which itself gradually or abruptly merges into the narrower intestine. The windings of the small intestine are connected by ligamentous tissue, and enclosed in a common sheath of peritoneum. In several of the Glyphodont Water-snakes (Homalopsinæ and Hydrophiinæ), the intestine is much convoluted; in Herpeton it is even longer than the body, although when coiled occupying only one-fourth of that length. The rectum is sometimes very short, sometimes rather long, and its anterior portion may have a short cæcum; it may be divided by transverse septa, with median or lateral perforation.

In snakes which swallow hard-shelled snails, the anterior part of the intestine has its inner wall furnished with zigzag muscular folds producing a reticulate appearance, followed farther down by transverse and then longitudinal folds. In these snakes the intestine is abruptly constricted behind the stomach, at which point the shells are broken or crushed after their contents have been digested; whilst in the egg-eating snakes, in which the eggshell has to be broken previous to its contents reaching the stomach, the oesophagus is narrowed in front of the latter, at the point where the tooth-like ventral processes of the vertebræ project and pierce the wall of the œsophagus in order to aid in this function, after which the broken shell is rejected through the mouth.

The more or less elongate, feebly-lobed kidneys are placed in the posterior part of the body, often extending nearly to the cloaca; the right is usually a little longer than the left, or extends a little farther forward, or even may commence where the other ends. The suprarenal bodies are narrow and elongate, placed on the renal veins or on the vena cava inferior.

The ureters leave the hind ends of the kidneys, and open through the side-walls of the cloaca on a papilla which in the males contains also the opening of the vas deferens. There is no urinary bladder. The genital organs will be mentioned in the next chapter. The liver is usually long and narrow, measuring one-fifth to one-fourth the length of the body, on the right side of the alimentary canal, commencing just behind the heart or farther back. It is exceptionally short in Chersydrus. It is sometimes divided by transverse furrows. Its posterior extremity is bilobate, and the left lobe usually extends beyond the right, although the reverse has been observed in some snakes. The gall-bladder, which may be absent, is remarkable for its distance from the liver. The pancreas, elongate but comparatively small, is located near the spleen, on the left side of the alimentary canal, at a considerable distance from the liver.

The peritoneal part of the body-cavity is subdivided into a number of spaces or cœlomic compartments enclosed in serous capsules—viz., a posterior or intestino-genital, a gastric on the left side, and a pair round the liver, corresponding to its two lobes.

Fat-bodies are much developed, either in the form of small separate lobes, or as a continuous, much folded band, on each side of the body.

CHAPTER IX
ORGANS OF REPRODUCTION; PAIRING; OVIPOSITION; DEVELOPMENT

The genital glands are situated anterior to the kidneys, the right extending farther forward and often larger than the left. The testes are elongate. The vas deferens is closely folded proximally, and runs along the outer side of the kidney into the cloaca close to the ureter. The ovaries are elongate, and consist of two lamellæ, with a lymph-space between them. The oviduct extends from near the anterior extremity of the ovary to a common chamber, or vagina, which is above the rectum and opens into the cloaca; this vaginal chamber may be more or less completely divided into two.

The males are provided with a pair of intromittent organs, or hemipenes, each connected with one of the caudal vertebræ by a muscle (retractor penis) which often exceeds it in length. These organs are cylindrical or club-shaped and hollow, with the inner surface divided into numerous cavities and beset with papillæ, and usually also with hard spines, of which those towards the apex may be greatly developed, folded against the walls, and directed towards the extremity. Such spines are absent in the snakes provided with claw-like rudiments of hind limbs. The cavities of the hemipenis are connected by a branch with the dorsal artery, and it is by a flow of blood into them that erection of the organ is accomplished. Each hemipenis is lodged in a cavity on each side of the base of the tail; when protruded it turns inside out, and the inner surface becomes the outer, the papillæ and erected spines serving to maintain a firm hold in the vagina, from which the organ cannot be withdrawn except by invagination. It has been observed that the presence of spines on the hemipenis is associated with much tougher vaginal walls. The organ is grooved along its entire length, the groove being the sulcus spermaticus, which, when the edges of the two hemipenes meet, forms with its fellow a canal to convey the semen into the oviduct; this sulcus may be bifurcate, as in the Viperids and some Colubrids.

Anal pockets, secretory organs on each side of the vent and lodged in the base of the tail, seem, in females, to be the homologues of the hemipenes; but this view cannot be held, since the same organs are present, though smaller, in males also, situated dorsally to the hemipenes. The glands with which they are provided produce the strong and offensive odour which appears to be a means of defence in our Grass-snake and other species, and which also serves to bring the sexes together, the glands being more active during the breeding season. A Viper-catcher in France is said to obtain good results by rubbing his boots with these glands, as a means of attracting the snakes in the spring.

In European species pairing takes place in spring, sometimes again at the end of summer or in autumn. After hibernation the testes of the males are rather voluminous, and the sperm-ducts are often full of spermatozoa. The male gets alongside the female, sometimes seizing her round the neck with his jaws, and remains stretched out against her or twists the posterior part of his body in a few coils around hers. In the Vipers the bodies of the pairing individuals are completely entwined. The male then endeavours to bring the two anal orifices together, and when he has succeeded in getting the female to distend her cloacal opening, the intromittent organs are suddenly everted into the vagina. The union of the sexes sometimes lasts only a few minutes, but usually an hour or more; it has even been observed to last a whole day. Several copulations may take place at intervals of a few days. Many snakes are gregarious during the breeding season, and great numbers of males have been seen wriggling round the females, forming with their coils huge lumps or an entangled mass like a ball. The more or less prehensile tail with which thoroughly aquatic snakes, such as Hydrophis and Acrochordus, are provided, is no doubt of use in facilitating the pairing, when it has to take place in the water. Our European Water-snakes pair on land.

During the rutting season a slight pressure on the base of the male’s tail may cause the protrusion of the hemipenes, and so may a violent blow on the spine of the reptile. Thus, recently killed specimens of our Adder, with the organs everted, have more than once been taken by the ignorant for snakes with hind limbs, a mistake which must be pardoned when we remember that male embryos of the slow-worm and of snakes, in which the hemipenes are normally everted, have been described by zoologists, who should have known better, as examples showing external vestiges of limbs.

The spermatozoa soon make their way up the oviducts, in which the ripe ova have previously descended, or which gradually descend shortly after, these ducts becoming dilated in consequence. There are usually more eggs in the right than in the left oviduct, although the reverse has occasionally been observed.

Some snakes lay eggs shortly after impregnation, or a few weeks later; in others the young undergo their development within the oviducts, each enveloped in a thin, transparent, membranous capsule, which is torn immediately before or immediately after parturition, such species being termed “ovoviviparous.” Just before oviposition the female curves the base of the tail upwards, in order to extend the cloacal opening. The eggs are all produced together, usually at intervals of a few minutes, and generally adhere to one another by means of a sticky fluid secreted by the oviducts, thus forming a clump. In ovoviviparous snakes the young are born in succession, in the course of a few hours or of a few days. In many oviparous species it is the rule for freshly-laid eggs to contain more or less developed embryos, and Coronella punctata is said to produce thin-shelled eggs which hatch in less than half the time required for the eggs of its American congeners under the most favourable circumstances. There is thus almost every degree between oviparity and ovoviviparity.

These two modes of parturition bear no relation to the natural affinities of snakes. Thus, the European Coronella austriaca is ovoviviparous, and its North American congeners are oviparous; whilst, curiously, it is the inverse in the genus Tropidonotus. It was long believed to be an invariable rule for the Viperidæ to bring forth live young, the name Viper being derived from this well-known peculiarity, but it has now been ascertained that the South American Lachesis mutus, the Indo-Malay Lachesis monticola, and the African Causus and Atractaspis, lay eggs. All exclusively aquatic snakes, such as the Hydrophiinæ, are ovoviviparous, and thus dispensed from going on land for parturition.

The yolk entirely fills the eggshell; there is no albumen, or, if any exists, it is so much reduced as to easily escape observation. The eggshell in oviparous species contains a small amount of lime, and is not hard, but tough and parchment-like, white or yellowish; it is usually smooth, but in Pythons its surface is studded with minute pores, and in the American Zamenis constrictor it is rough, as if sprinkled over with loose grains of salt. The shape varies from a short oval to a long ellipse. It has been observed in some snakes that the eggs, on leaving the cloaca, are of an elongate shape, suggestive of a short cigar, and immediately after assume a more oval form. After they have been laid, the eggs absorb moisture and thus increase in size, especially in width; eggs which are at first twice as long as broad may be almost globular just before the birth of the young.

The number of eggs or young of one brood varies much according to the species, and also according to the age of the mother, large females usually producing a higher number and of a larger size than smaller specimens of the same species. Our European Zamenis, Coluber, and Coronella produce only 2 to 15; our Tropidonotus, 15 to 48; our Vipers, 3 to 22. Among exotics we may mention, as the most prolific, Bitis nasicornis, up to 47 young; Tropidonotus fasciatus, Abastor erythrogrammus, and Farancia abacura, 50; Lachesis lanceolatus, 60; Vipera russelli, 63; Boa constrictor, 64; Tropidonotus ordinatus, 78; Pseudaspis cana, 80; Python molurus, nearly 100 eggs.

The eggs are deposited in holes without any sort of nest, under moss or decomposing leaves, in accumulations of saw-dust, or in manure-heaps. In many cases it has been observed that the female remains for some time with her eggs or young, and in the large Pythons a sort of incubation takes place, the female remaining coiled in a spiral over the mass of eggs for six to eight weeks; an increase of several degrees in her temperature at that period has been ascertained by experiments conducted with every possible care, a remarkable fact in the case of a so-called “cold-blooded” animal.

The numerous reports of young snakes seeking refuge in their mother’s gullet have not been substantiated by satisfactory scientific evidence, and, although it is perhaps wise to say that the question remains an open one, it may be mentioned that, in Europe at least, trained observers who have devoted special attention to the habits of Vipers, in districts where these reptiles are exceedingly abundant, have never come across an instance of the form of maternal solicitude with which these snakes in particular have been credited. Not a single reported case of a female snake swallowing her young for protection rests on satisfactory evidence.

The embryo is closely coiled up in a spiral. Just before birth it is distinguished by a large, convex head, with large, prominent eyes, and a comparatively short body, the scales and ventral shields being much shorter than later in life. The umbilicus is situated in the posterior part of the body, from six to ten times as far from the head as from the vent. Long after birth the umbilical slit remains visible, and affords a means of distinguishing very young snakes from older examples of smaller species. In oviparous species the embryo is provided with a very conspicuous egg-tooth, pointing forwards and projecting from the notch in the lower border of the rostral shield; this egg-tooth is much reduced, and sometimes very indistinct, in the ovoviviparous species. The function of the egg-tooth is to cut through the tough eggshell. This, after the young has left it, shows one or several slits in its anterior extremity, cut as clean as if with a sharp knife. The egg-tooth becomes loose soon after birth, and is shed within a few hours or a few days, sometimes even before birth in ovoviviparous species.

Frequent cases have been observed of dicephalous embryos or young, which may live for a short time; there are even records of a three-headed snake, stated to have been seen at Lake Ontario, and of snakes with two heads and two tails.

Unless prematurely born with a considerable mass of vitellus attached to the umbilicus, the young immediately after birth resent all interference, hissing, snapping, or puffing themselves up, after the manner of their parents. The first shedding of the outer coating of the epidermis follows soon after birth; not before then does the young take to food.

No snake appears to be able to breed before it is four years old.

Well-authenticated instances of different species interbreeding are unknown, but specimens intermediate between Vipera berus and V. aspis, and between V. berus and V. ammodytes, have been assumed, with much probability, to be hybrids.

CHAPTER X
HABITS

Snakes may be grouped, according to their mode of life, in five principal categories, gradually merging into each other, or two of them not infrequently found combined in one and the same species. These categories are:—Ground-snakes, Sand-snakes, Burrowing-snakes, Tree-snakes, and Water-snakes.

Ground-snakes may be defined as living above ground, and only occasionally climbing bushes or entering the water. Among European genera, Coronella and Vipera are perfect examples of this type, whilst Coluber and Zamenis approach the Tree-snakes in often ascending bushes, or even trees.

Sand-snakes are adapted for living on loose sand, in which they seek concealment. Such are Lytorhynchus and some Psammophis among the Colubridæ, Cerastes among the Viperidæ. Eryx connects this category with the next.

Burrowing-snakes live chiefly underground, and often have the visual organ atrophied in consequence, as in Typhlops; all the Typhlopidæ, Glauconiidæ, and Uropeltidæ, belong to this category; the Viperid Atractaspis is also a burrowing type.

Tree-snakes spend the greater part of their life on bushes or trees. Corallus among the Boidæ, Dendrophis and Dendraspis among the Colubridæ, Atheris and various species of Lachesis among the Viperidæ, may be quoted as examples.

Of Water-snakes, some are exclusively aquatic, like the marine Hydrophiinæ and the typical Acrochordinæ (Acrochordus, Chersydrus) and Homalopsinæ (Hipistes, Herpeton). Chersydrus and Hipistes occur in the sea as well as in fresh water. Many species of Tropidonotus (T. tessellatus and T. viperinus in Europe), as well as the genera Helicops, Grayia, Boulengerina, etc., among the Colubridæ, Eunectes among the Boidæ, Ancistrodon piscivorus among the Viperidæ, are chiefly but not exclusively aquatic.

Our Tropidonotus natrix stands between the Ground-snakes and the Water-snakes; Boas and Pythons are as much Water-snakes as Tree-snakes. As shown by these and many other examples which might be given, a division into categories cannot always be applied with precision, nor does it convey an expression of the natural relationships of the species, as was believed by many systematists of the last century, who appealed to such adaptations for the definition of families.

A vertical pupil denotes more or less nocturnal habits. Nevertheless our European Vipers, which are provided with such a contractile pupil, are far from exclusively nocturnal, delighting to bask in the sun, and pairing and feeding in the day-time. The Boidæ appear to be more nocturnal, but no snake is known to be absolutely so, and the two species of Coluber which have been found living in perfect darkness in limestone caves in the Malay Peninsula and China, where they feed chiefly on bats, occur also outside the caves, and probably never breed in them.

It is often stated in books that the organs of locomotion for the exceedingly elongate body of snakes are the ribs, and these creatures have even been compared to Centipedes. This statement is no doubt true to a certain extent for slow locomotion on uneven ground, when the ribs and the corresponding ventral shields afford a point of support; but it does not account for the rapid movements, as when a snake darts like an arrow in pursuit of its prey or to escape from an enemy. Besides, the winding motions are not different from those of a Slow-worm or Glass-snake, in which, encased as they are in a bony armour, the ribs cannot come into play at all. The action of the muscles alone is quite sufficient to account for the reptation of snakes, without the ribs having to play an essential part.

Not only the Cobras, but several harmless snakes, are able to raise the anterior third of the body vertically, when taking up a threatening attitude in the presence of an enemy, at the same time widening or inflating the region behind the head.

Most snakes can climb, and in this case the ribs and ventral shields are of great assistance. The Tree-snakes, usually characterized by a very slender, sometimes compressed, body, or by a prehensile tail, are specially adapted for twining themselves round branches, and in several of them the presence of a keel on each side of the ventral and subcaudal shields, accompanied by a notch corresponding to the keel, affords an additional help for climbing on vertical uneven surfaces, such as the trunks of trees. This condition of the ventral shields has a bearing on the extraordinary mode of locomotion with which some Tree-snakes (Chrysopelea, and probably also Dendrophis) have long been credited by the Malays. We allude to the so-called Flying-snakes, remarkable for their habit of shooting down from trees and descending to the ground at an oblique angle, the body being kept rigid the whole time of the “flight.” It has been observed in Chrysopelea that the ventral surface between the lateral keels, which may be compared to hinges, can be drawn in and become deeply concave, whilst at the same time a slight dorso-ventral flattening of the body takes place. During this muscular contraction the snake is like a piece of bamboo bisected longitudinally, and is buoyed up in such a way as to explain its parachute-like descent.

All snakes are able to swim, and the more aquatic kinds may spend a few hours under the water. A Python molurus is known to have remained alive in a basket sunk for thirty-six hours in a river. The best adapted for aquatic life are the Hydrophiinæ, or Sea-snakes, most of which never leave the water, and are quite helpless and soon die when brought on shore; their body is more or less compressed posteriorly, and the tail oar-shaped. Sea-weeds and barnacles sometimes settle on them. Algæ have also been observed growing on the fresh-water snake Herpeton tentaculatum.

As regards food, Burrowing-snakes, as well as a few small Ground-snakes, subsist mostly on worms, insects, and myriopods; Tree-snakes on lizards, frogs, birds and their eggs; Water-snakes on fishes and batrachians. Among the other types, some show a predilection for mammals, others for lizards or snakes, whilst not a few feed indiscriminately upon mammals, birds, reptiles and batrachians, even on slugs, insects, and worms, in addition. However surprising, it is a fact that spiny mammals are occasionally eaten, spines of the Madagascar Hedgehog (Ericulus) having been found in the excrements of a Boa madagascariensis. Even hard-shelled eggs and molluscs may constitute the principal or exclusive food of certain snakes.

Thus, Dasypeltis eats nothing but birds’ eggs, the shells of which are crushed in the gullet, by a special contrivance mentioned above (p. [80]), and are soon after rejected through the mouth as a pellet. Other snakes, such as Coluber and Lioheterodon show themselves partial to eggs in addition to live prey, but their alimentary canal does not depart from the normal, the eggs being broken in the stomach and the remains of the shells passed with the excrements.

The Amblycephalidæ subsist almost entirely on snails and slugs, the shells of the former being crushed in the anterior part of the intestine after their contents have been digested, and the débris are rejected through the vent. A small land tortoise has been found in the stomach of a Cobra (Naia haie) from Algeria.

Snakes which take large prey secure it according to three methods: By catching it simply with the jaws, and immediately proceeding to swallow it, as in Tropidonotus and in some of the Constrictors when dealing with small animals; by constriction, after having seized it with the jaws, crushing it in the coils of their body and thus killing it previous to feeding, as in the Boidæ and Coluber; or by poisoning, by a mere stroke with the fangs, the result being awaited before the meal is begun, as in most of the Viperidæ. Other poisonous snakes proceed according to the first method, the use of the venom being to reduce the struggles of the victim and to relax its muscles. Such snakes as are in the habit of previously killing their prey show little reluctance to accept dead food in confinement, a thing which others usually refuse to do; they may, however, be deceived by the dead animal being agitated before them, and the system now adopted in our Zoological Gardens, of offering all snakes previously-killed animals, has been attended with comparative success.

Some species feed almost exclusively on other snakes, and often manage to swallow individuals as large as, or even a little larger than, themselves. Examples are known of harmless snakes showing a predilection for dangerous species, to whose poison they are immune (see p. [71]).

As a rule snakes that eat fish will also eat batrachians, but nothing higher in the scale, although exceptions have been reported, such as the Anaconda feeding on mammals, birds, reptiles, and fish, and our Grass-snake having taken mice and birds. Some that feed chiefly on lizards and snakes will occasionally eat also mammals, and vice versa, but rarely frogs. On the other hand, European Vipers accommodate themselves to a more varied bill of fare, being known to feed on mammals, birds, reptiles, batrachians, insects, and slugs, and they have even been observed to eat voles showing signs of putrefaction.

The enormous prey which some snakes are able to swallow is quite astounding. Anacondas and Pythons, the largest snakes, have been known to swallow calves and good-sized antelopes with their horns, animals which, even after being somewhat crushed by constriction, very much exceed the calibre of the snake. A Python molurus 17 feet long is reported on good evidence to have swallowed a gravid Axis deer. A Grass-snake half an inch in diameter can manage a frog or toad three times that width, and a Dasypeltis of the same size a hen’s egg. Such feats are rendered possible by the mobility of the jaws and palato-pterygoid arch on the cranium, and the elasticity of the ligaments by which they are attached (see above, p. [42]), as well as by the mobility of the ribs and the absence of sternal apparatus, together with the great distensibility of the skin. When a snake proceeds to dispose of a large prey, which, if it be a mammal or bird, is usually seized head-first, it pulls itself forward by alternate movements of the jaws, the maxillary and the mandibular ramus of the one side, and then of the other, being extended anteriorly and laterally, the snake at the same time producing an abundant salivation which renders the prey very slimy. Several repeated alternate movements of the jaws bring the head of the prey to the gullet, where the muscles and ribs come into play, and the two sides of the jaws work no longer alternately, but together. When once in the œsophagus, the prey progresses with much greater facility, and usually reaches the stomach in a few minutes, whilst the previous process of deglutition may have lasted half an hour. While this laborious operation is going on, the breathing of the snake is not impaired owing to a remarkable contrivance: the trachea can be protruded in such a manner as to bring its opening outside the mouth.

In cases where the victim is eaten alive, the snake has to contend with its struggles, but retrogression is rendered impossible by the backwardly-directed sharp teeth with which the jaws and palate are beset. A frog is usually caught by one of the hind limbs and swallowed back-first, the long hind limbs stretching forwards as they fold against the body; its struggles are often still apparent when it has reached the œsophagus. Snakes when caught immediately after a meal are in the habit of disgorging their food, and it sometimes happens that a frog or toad is thus vomited alive. An instance is known of a naturalist having captured a Grass-snake and put it in a linen bag. On opening it a short time after, great was his surprise to find the snake had escaped through a small hole in the bag, leaving instead a living toad too big to pass through the hole.

If not of too large a size, several animals will often be swallowed in rapid succession, after which the gorged snake will allow its digestive organs several days, or even weeks, of repose. A large Anaconda in the Paris Jardin des Plantes fed only thirty-six times in the course of seven years. Digestion is usually rapid in the small snakes, defecation taking place twenty-four to forty-eight hours after the feeding; it lasts much longer in the large Boas and Pythons. Thus, in the above-mentioned Anaconda it has been observed to take from nine to thirty-eight days. Even the hardest bones of birds are decomposed by the gastric juices, but hairs, feathers, and horny productions, are passed with the excrements, sometimes forming regular balls. It is in most cases possible to tell, from an inspection of the dried fæces, what a snake has been feeding on, hairs, feathers, beaks, claws, epidermal horny shields, bits of tooth-enamel, being found mixed with the chalky matter which represents the decomposed bones. As a rule there is but one defecation after each meal, but there are in addition more frequent renal dejections, consisting chiefly of uric acid.

In captivity snakes show themselves capricious in the choice of food, one individual preferring mammals, whilst another, of the same species, will only take birds; and many, although to all appearances perfectly healthy, will persist in refusing all food, and allow themselves to die of starvation—a suicide which may require months, or even years, to accomplish. A Rattle-snake in the menagerie of the Jardin des Plantes in Paris has lived two years and two months without taking any food, a Python sebæ nearly two years and a half, a Boa madagascariensis four years and a month. A Viper aspis was kept for three years without food and without losing its vicious temper. Specimens thus fasting do not, as a rule, renew their epidermis, or do so but very rarely. Our Common Adder can very seldom be induced to feed in captivity. Other snakes may rid themselves of all shyness to the extent of taking food from the hand, or show such appetite as to seize a prey immediately on being released from the small box or bag in which they have travelled for a considerable time.

Most snakes drink, and pretty often—not by lapping with the tongue, but by drawing in water from the mouth and immersing the anterior part of the head. Some are said to be fond of milk, but there is no foundation for the belief held by peasants, that they enter sheds with the object of sucking milk from the cows, which would be a material impossibility; their real purpose in visiting such places being a search for suitable dung-heaps in which to deposit their eggs.

Snakes cannot be credited with much intelligence or educability, nor do they display any very marked instincts. The least stupid and most easily tamed are the species of the genera Coluber and Coronella. There is, however, considerable difference in this respect between individuals of the same species. Most snakes, when freshly caught, defend themselves by biting, and some individuals retain their savage temper after months of captivity; others hardly ever bite, even if molested. The Common Grass-snake, for instance, hisses loudly and takes up a very threatening attitude, or even pretends to snap with open mouth, but very seldom bites; its principal defensive action when caught consists in voiding a most repulsive secretion from its anal glands, which it evidently controls, as it ceases doing so when accustomed to being handled. The same snake also produces, during the spring, an oily exudation from the skin which has the same repulsive smell. Mr. H. N. Ridley has observed a Malay snake allied to Tropidonotus, Macropisthodon rhodomelas, to exude drops of a white viscid liquid from the skin of its neck, which is flattened out like that of a Cobra when in an attitude of defence, and he noticed that his dog, seizing the snake to worry it, foamed at the mouth as if he had been biting a toad.

The hissing is produced by the rapid expulsion of air from the lungs through the trachea and the notch at the end of the mouth, which is kept shut at the time. Snakes provided with an epiglottis (see p. [79]) produce a much louder hissing. Other sounds are produced by some snakes. Thus, the Indian and African Vipers of the genera Echis and Cerastes make a curious, prolonged, rustling noise, by rubbing the folds of the sides of the body against one another. This sound is produced by friction between the serrated keels of the lateral scales, which are disposed obliquely with their tips directed downwards and backwards; the noise can even be repeated after the death of the animal, by twisting the body and thus rubbing or rasping these little saws against one another. The same thing probably takes place in the African genus Dasypeltis, in which we find a similar arrangement of the scales, though to a less degree.

The best known sounding apparatus is that of the Rattlesnakes, described on p. [20]. When alarmed, these snakes gather the body in a few coils or roll themselves up in a spiral, with the tail erect in the centre, and vibrating with great rapidity, whilst the head is ready for attack. Other snakes, such as the Ancistrodon and some species of Coluber and Zamenis, when excited, vibrate the tail in the same manner; but, being deprived of the sound-producing apparatus, this expression of their anger does not attract the same attention. It is from such a habit, however, that the rattle must have been evolved and perfected, not necessarily in a Lamarckian sense, but through the different steps by which evolution or creation has proceeded; Natura non fecit saltus, as Linnæus well said. Many suggestions have been made as to the use of the rattle. One of them is that the rattling resembles the sound made by locusts, and serves to decoy insect-eating birds; another, that it serves to call the sexes together. Probably it is useful to the snake as a warning to keep off disturbers which cannot serve as food, and thus prevents useless expenditure of venom, or even the breaking of the fangs. At any rate, it gives expression to the snake’s excitement, as does the voice in the case of many other animals, and it seems reasonable to suppose that it may be applied to different purposes. With the advent of man, this means of attracting attention must tend to the more rapid extermination of the snakes which possess it.

Another curious behaviour is that of feigning death, as observed in a harmless but vicious-looking snake, Heterodon, often called Puff-adder in America. It looks more like a Viper than a harmless snake, and when disturbed hisses loudly and flattens out the anterior part of the body, much as does a Cobra, and pretends to strike, although it is one of the few snakes that never bite man. If, however, this display proves of no avail in frightening away the intruder, the snake rolls on its back and opens its mouth, and then lies for a time, which may exceed a quarter of an hour, absolutely motionless, as if dead. As soon as it thinks the danger over, it awakens from its spasm and rapidly moves off. It is the opinion of those who have most experience of this snake that this extraordinary behaviour is not to be explained as a convulsion or faint due to fright, but constitutes a deliberate trick to save its life. Individuals of the South African Ringhals (Sepedon hæmachates) and of the Common Grass-snake have also been observed to feign death.

The notion that snakes fascinate their prey, attracting it or reducing it to immobility by a mysterious power in their glittering eyes, is pure fable. Animals placed in a cage with a snake evince no particular fright, and fly away when pursued, if not actually turning round to defend themselves. It is even dangerous to offer a good-sized snake a wild rat for food, as all keepers of menageries know.

In cold and temperate climates snakes hibernate, lying more or less torpid in holes or hollow trees, sometimes assembled in numbers and coiled together in a mass. The first thing they do in awakening in the spring is to cast the outer coating of the epidermis, as described above (p. [20]). Several exuviations take place during the period of activity, sometimes pretty regularly every month, sometimes at very irregular intervals. A few days previous to this operation the snake is languid and abstains from feeding; its skin is dull and the sight impaired by the opaque condition of the lid; a day or two before moulting, the outer stratum of the epidermis becomes again transparent and the eye clear, through this stratum becoming detached from the subjacent tissue, until it is pulled off in one piece, by the snake rubbing itself against stones or bushes. The first exuviation takes place very shortly after birth.

Snakes are long-lived, although the limit of duration of life is not known in any of them. They grow slowly, and do not appear ever to reach sexual maturity until the fourth year, when they continue increasing in size for a long period. A Python reticulatus and an Ancistrodon piscivorus are reported to have lived twenty-one years in captivity in Paris. The young of many snakes are very secretive, and are not often found in the open, those that are met with being as a rule either new-born or approaching sexual maturity.

Snakes are tenacious of life, and remarkable for the reflex movements which take place after they have been cut to pieces, the severed parts of the body and tail wriggling for a considerable time, and the head endeavouring to bite. Accounts of decapitated Rattlesnakes turning round and striking with their bloody stumps are probably not snake stories.

CHAPTER XI
PARASITES

Like all other animals, snakes are infested with a multitude of vegetable and animal parasites, both external and internal. About 300 species of Ophidian parasites have been recorded; yet our knowledge of them is very imperfect. Although some 2,000 species of snakes are known, parasites have not been recorded for more than 168 species, and in the great majority of these (102) only a single parasite: a tick, a hæmogregarine, or some intestinal worm. Owing to the more frequent opportunity of dissecting them, the common menagerie snakes have yielded better records, notwithstanding the fact that they usually lose most of their parasites through constant handling, prolonged fasting, and artificial surroundings. Thus, we have a list of thirteen species for the Indian Python molurus, and one of twenty-two species for the Boa constrictor. But no systematic search appears to have been attempted, save, perhaps, in the case of a few European species.

It is interesting to notice that it was the finding of an Ophidian parasite which prompted Francesco Redi to write his famous “Observations on the Living Animals which are found within Living Animals.” This work, a veritable treatise of comparative parasitology, published in 1684, caused the great naturalist, physician, and poet to be regarded as the father of that science. He tells us that in dissecting a curious dicephalous Vipera aspis, caught at Pisa, he found within the intestines a number of roundworms (Ascaris cephaloptera), and on the surface of one of the two lobes of the liver five cysts enclosing a small worm, which he rightly ascribed to the same species.

The parasites of snakes are here enumerated by Dr. L. W. Sambon, in systematic order.

Arthropoda.—Two families of the class Arachnida, the Ixodidæ and the Linguatulidæ, furnish numerous species parasitic on snakes.

Of the Ticks (Ixodidæ) we find, as a rule, species of the genera Amblyomma and Aponomma, the latter genus being almost entirely confined to Reptiles. A single species of the genus Hæmaphysalis (H. punctata, Can. and Franz, 1877) has been reported once from Vipera aspis. A few larval forms found on various snakes have been reported under the generic name Ixodes, but they probably belong either to Amblyomma or Aponomma.

The Ophidian Tick-parasites, like those of mammals, birds, lizards, and tortoises, appear to be in many cases the means of transmission of protozoal infections from snake to snake.

The Tongue-worms (Linguatulidæ) are, without doubt, of the greatest possible interest. Their systematic position has ever been a puzzle to zoologists, and even now is a matter of controversy. They have been looked upon as Hirudinea by Winsberg (1765), Cestoda by Chabert (1787), Acanthocephala by Humboldt (1808), Trematoda by Rudolphi (1809), and Nematoda by Nordmann (1832). It was Van Beneden (1848) who first recognized their Arthropod nature, but he placed them amongst the Crustacea. Schubärt (1853) suggested that their proper position is amongst the Mites (Acarina), and Leuckart (1860) adduced important anatomical and embryological evidence in support of this view, which was confirmed by Railliet in 1883 and by Sambon in 1910.

No less than three out of the four genera of Linguatulids so far established are represented by species parasitic on snakes. They are the genera Porocephalus, Reighardia, and Raillietiella.

The genus Porocephalus is of special interest, because some of its species, such as Porocephalus armillatus, a parasite of African Pythons (Python regius, P. sebæ) and Puff-adders (Bitis arietans, B. nasicornis, B. gabonica), and Porocephalus moniliformis, a parasite of Oriental Pythons (Python molurus, P. reticulatus), are, in their nymphal stage, deadly parasites of mammals, including man.

The genus Reighardia was established by Professor H. B. Ward, in 1899, for a Linguatulid of gulls and terns, first described, in 1861, by De Filippi. In 1910 Sambon included in this genus other similarly structured Linguatulids from crocodiles, monitors, and snakes.

The genus Raillietiella was established by Sambon in 1910 for a Linguatulid (Raillietiella boulengeri) of the African Puff-adders (Bitis arietans, B. gabonica). Amongst the characters of this genus is one of great structural and phylogenetic importance—viz., the position of the female sexual orifice at the anterior end of the abdomen, whilst in the other known genera it is at the posterior extremity.

According to Prowazek, Sambon, and Laveran, the Ophidian Linguatulids, which live as blood-suckers in the air-passages of their hosts, are able to foster and transmit the hæmogregarines of these hosts.

Acanthocephala.—The early encysted stages of several species of Thorn-headed worms (Acanthocephala), belonging to the family Echinorhynchidæ, have been reported from snakes belonging to very different genera, such as Boa, Tropidonotus, Zamenis, Drymobius, Xenodon, Dipsadomorphus, Oxyrhopus, Erythrolamprus, Diemenia, Naja, Elaps, Vipera, Lachesis. Their further development probably occurs in ophiophagous birds. Thus, Echinorhynchus oligacanthoides, Rud., the immature stages of which occur encapsuled within the body cavity of Lachesis lanceolatus and other neotropical snakes, when adult is found attached to the intestinal mucosa of Milvus bidentatus.

Nematoda.—The roundworms (Nematoda) so far described from snakes belong to the families Ascaridæ, Strongylidæ, Trichotrachelidæ, and Filariidæ. Some of the genera belonging to these families, such as Cucullanus, Nematoxys, Oxysoma, are as yet represented by a single species in a single host; others, such as Ascaris, Polydelphis, Heterakis, Strongylus, Diaphanocephalus, Physaloptera, Trichosoma, number already several species more or less widely distributed.

Eelworm infection (ascariasis) is very common in snakes, and not infrequently the infection is a heavy one; Sambon twice found over fifty specimens of Polydelphis in Puff-adders (Bitis arietans). This investigator has shown that the snake eelworms undergo an encysted stage of development within the body cavity of their hosts before migrating into the intestinal lumen for the purpose of fertilization and oviposition. Thus, Redi was quite right in considering the immature, encysted forms found in one of the livers of his double-headed Asp as belonging to the same species of eelworm (Ascaris cephaloptera) as that which the snake harboured in its intestine.

Professor A. Railliet, whilst examining specimens of Polydelphis which had been preserved for nearly two months in a 3 per cent. solution of formalin, found that the ova within their uterine tubes had undergone development, and still contained living embryos; indeed, some of these hatched under the microscope, and moved very actively in the preserving fluid. This is in no way surprising, because even after several years of preservation in formalin solution the embryos of other species of eelworms (Ascaris equorum, A. marginata) have been found in a living condition.

Trematoda.—The Flukes (Trematoda) of snakes, so far described, belong to the following genera: Agamodistomum, Astiotrema, Brachylaimus, Cotylotretus, Dicrocœlium, Diplodiscus, Distoma, Halipegus, Lecithodendrium, Metorchis, Opisthogonimus, Opisthorchis, Plagiorchis, Saphedera, Telorchis, Tetracotyle, Zeugorchis.

Cestoda.—Save a few larval forms (Cysticercoides, Piestocystis, Sparganum), the known tapeworms (Cestoda) of the Ophidia belong to the genera Bothridium and Proteocephalus.

Protozoa.—Numerous species of Hæmogregarines have been described from snakes. As a rule the forms seen in the peripheral blood are sporonts, the schizogonic cycle occurring in the lungs. The sporonts do not greatly alter their host cells; they are invariably doubled up within a more or less thick capsule. Some species show a marked sexual differentiation, others not. Trypanosomes, Spiroechaudinniæ, and Plasmodidæ have also been described from the blood of various snakes.

Within the alimentary tube have been found species of Trichomonas and Caryospora.

Bacteria.—Acid-fast bacilli have been described in tubercular lesions found in snakes by Sibley, Gibbs and Shurley, Shattock, Hausemann, and Sambon.

The so-called “canker,” which so frequently develops in the oral cavity of captive snakes, is also a bacterial disease, due to a specific bacterium of thick, rod-shaped form.

LIST OF PARASITES HITHERTO
RECORDED FROM EUROPEAN SNAKES

TROPIDONOTUS NATRIX, L.

Acanthocephala.

Echinorhynchus inæqualis, Rudolphi.
Echinorhynchus polyacanthus, Creplin.

Nematoda.

Strongylus auricularis, Zeder.
Strongylus catanensis, Rizzo.
Trichosoma mingazzini, Rizzo.
Oxysoma brevicaudatum, Zeder.
Nematoxys commutatus, Rudolphi.
Ascaris cephaloptera, Rudolphi.

Trematoda.

Opisthorchis caudatum, Polonio.
Dicrocœlium assula, Dujardin.
Diplodiscus conicum, Polonio.
Tetracotyle colubri, v. Linstow.
Distoma acervocalciferum, Gastaldi.
Distoma allostomum, Diesing.
Distoma nematoides, Mühling.
Saphedera naja, Rudolphi.
Brachylaimus signatum, Dujardin.
Telorchis ercolanii, Monticelli.
Lecithodendrium nigrovenosum, Bellingham.
Plagiorchis mentulatus, Rudolphi.

Cestoda.

Ligula panceri, Polonio.

TROPIDONOTUS TESSELLATUS, Laur.

Nematoda.

Strongylus denudatus, Rudolphi.
Physaloptera abbreviata, Rudolphi.
Physaloptera striata, v. Linstow.

Trematoda.

Plagiorchis mentulatus, Rudolphi.

TROPIDONOTUS VIPERINUS, Latr.

Acanthocephala.

Echinorhynchus lobianchii, Monticelli.

Trematoda.

Distoma allostomum, Diesing.
Opisthorchis caudatum, Polonio.
Telorchis ercolanii, Monticelli.
Astiotrema monticellii, Stossich.

Cestoda.

Ligula pancerii, Polonio.

Protozoa.

Hæmogregarina viperina, Billet.

ZAMENIS GEMONENSIS, Laur.

Acanthocephala.

Echinorhynchus cinctus, Rudolphi.
Echinorhynchus polyacanthus, Creplin.
Echinorhynchus heterorhynchus, Parona.

Nematoda.

Strongylus catanensis, Rizzo.
Filaria parvomucronata, Rizzo.
Trichosoma sonsinoi, Parona.

Trematoda.

Distoma subflavum, Sonsino.
Brachylaimus baraldii, Sonsino.
Saphedera naja, Rudolphi.

Cestoda.

Cysticercus acanthotetra, Parona.
Cysticercoides rostratus, Mingazzini.

COLUBER QUATUORLINEATUS, Lacep.

Acanthocephala.

Echinorhynchus oligacanthus, Rudolphi.

Nematoda.

Ascaris cephaloptera, Rudolphi.

Trematoda.

Plagiorchis sauromates, Poirier.

Protozoa.

Hæmogregarina, sp.

COLUBER LONGISSIMUS, Laur.

Protozoa.

Hæmogregarina colubri, Börner.

CORONELLA AUSTRIACA, Laur.

Nematoda.

Tricheilonema megalochilum, Diesing.
Physaloptera colubri, Rudolphi.

Cestoda.

Piestocystis dithyridium, Diesing.

Protozoa.

Monocercomonas colubrorum, Hammersch.

CORONELLA GIRONDICA, Daud.

Protozoa.

Hæmogregarina coronellæ, França.

VIPERA BERUS, L.

Nematoda.

Physaloptera dentata, v. Linstow.

Trematoda.

Agamodistomum viperæ, v. Linstow.
Tetracotyle colubri, v. Linstow.

VIPERA ASPIS, L.

Arthropoda.

Hæmaphysalis punctata, Can. & Franz.

Acanthocephala.

Echinorhynchus cinctus, Rudolphi.

Nematoda.

Ascaris cephaloptera, Rudolphi.
Diaphanocephalus viperæ, Rudolphi.

Protozoa.

Caryospora simplex, Léger.
Hæmogregarina samboni, Giordano.

VIPERA AMMODYTES, L.

Nematoda.

Ascaris ammodytis, Rudolphi.
Ascaris cephaloptera, Rudolphi.

CHAPTER XII
DISTRIBUTION

Representatives of the order Ophidia are found over the whole world, with the exception of Iceland, Ireland, and New Zealand, between the Northern limit of 67° in Europe (Vipera berus), 60° in Asia (Vipera berus), and 52° in America (Tropidonotus ordinatus), and the Southern limit of 44° (Philodryas schotti). The highest altitudes reached by them are 14,000 feet in the Himalayas (Tropidonotus baileyi), 9,700 feet in the Alps (Vipera aspis), and 9,000 feet in the Andes (Liophis albiventris). They are most numerous between the tropics, and the number of species gradually diminishes to the North and South.

For the purpose of showing the distribution of the principal groups, we will follow the divisions into families and subfamilies enumerated above (p. [4]).

Typhlopidæ.—S.E. Europe, S. Asia, Africa, Australia (exclusive of Tasmania), C. and S. America, and W. Indies.

Glauconiidæ.—S. Asia (as far E. as Sind), Africa (exclusive of Madagascar), C. America (extending into the S. parts of N. America), S. America.

Pythoninæ.—S. Asia, Africa (exclusive of Madagascar), Australia (exclusive of Tasmania), C. America.

Boinæ.—S.E. Europe, C. and S. Asia, N. Africa, Madagascar, Mauritius, W. Polynesia, S.W. of N. America, C. and S. America, and W. Indies.

Ilysiidæ.—S.E. Asia, S. America.

Uropeltidæ.—India and Ceylon.

Xenopeltidæ.—S.E. Asia.

Acrochordinæ.—S.E. Asia, C. America.

Colubrinæ.—The whole range of Ophidia, except Tasmania.

Dasypeltinæ.—Africa (exclusive of Madagascar).

Homalopsinæ.—S.E. Asia, N. Australia.

Dipsadomorphinæ.—S. Europe, C. and S. Asia, Africa, Australia (exclusive of Tasmania), C. America (extending into the S. parts of N. America), S. America.

Elachistodontinæ.—India.

Hydrophiinæ.—Indian and Pacific Oceans.

Elapinæ.—S. Asia, Africa (exclusive of Madagascar), Australia and Tasmania, Fiji Islands, C. America (extending into the S. parts of N. America), S. America.

Amblycephalidæ.—S.E. Asia, C. and S. America.

Viperinæ.—Europe, Asia, Africa (exclusive of Madagascar).

Crotalinæ.—S.E. Europe, Asia, America.

The Zoogeographical Regions into which the world is usually divided (Palæarctic or Europo-Asiatic, Oriental or Indian, Ethiopian or African, Australian, Nearctic or North American, Neotropical or South American) do not lend themselves any better than the ordinary divisions of physical geography to the study of the distribution of Snakes. Contrary to what we find in dealing with the Tortoises, Australia does not show any special affinity to South America, and, as in the case of the Lizards, it must be regarded as an impoverished extension of the Indo-Malay fauna; as with the Lizards, also, Europe and Africa hang together, whilst Madagascar stands apart, distinguished by many negative features and some points of agreement with South America (Boidæ). There is a greater difference between the Snakes of Europe and those of Eastern Asia than there is between the latter and those of North America, whilst in Lizards a primary distinction must be made between the Old World and the New. Southern Asia east of Persia (the Oriental Region) is the great Ophidian centre, all the groups mentioned above, with the exception of the Dasypeltinæ, having representatives within its limits, and a large and very distinct family, the Uropeltidæ, being confined to it. The Pythoninæ occur along with the Boinæ, the Viperinæ with the Crotalinæ, and the Elapinæ are represented by varied forms, as they are also in Africa and still more in Australia, where they form the overwhelming majority, and in some parts, as well as in Tasmania, the exclusive Ophidian population. The coasts of India and Malaya are also the home of the great majority of the Hydrophiinæ. Large genera like Tropidonotus, Zamenis, and Coluber, extend over the Europo-Asiatic and North American regions, but they are equally well represented in the Oriental. The great difference between Madagascar and Africa is, as we have said, very striking. Madagascar possesses Boidæ generically identical with those of South America, but otherwise only Typhlopidæ, Colubrinæ, and Dipsadomorphinæ; whilst in the greater part of Africa the Boinæ are replaced by the Pythoninæ, and the Glauconiidæ, Elapinæ, and Viperinæ are generally distributed. North America agrees with Asia and South America in its Crotalinæ, otherwise its Ophidian fauna is not very different from that of Europe, although much richer, and South America shares the Glauconiidæ with Africa and the Ilysiidæ with Southern Asia. South America is rich in Colubrinæ and Dipsadomorphinæ, nearly all generically different from those of other parts of the world, and the Elapinæ are represented by the single genus Elaps, with many species, two of which extend to the southern parts of North America.

This rapid sketch of the principal facts of Ophidian distribution suffices to show how difficult it would be to frame geographical regions that would give expression to these facts. Such regions would necessarily be very different from those adopted in dealing with the distribution of the other divisions of the class Reptilia. This is a task which need not be attempted on the present occasion.

A few words as to the salient characters of the European fauna, which is a poor one as compared with other parts of the world. The single species of the genera Typhlops and Eryx must be regarded as outposts from South-Western Asia; the single species of Ancistrodon, which extends from Central Asia into a very small territory to the south-east, is also an Asiatic type. The genera Tropidonotus, Zamenis, Coluber, Coronella, and Contia, are characteristic of the Northern Hemisphere, and the first three are, besides, equally well represented in the Oriental region; a few species of Tropidonotus are also found in Africa and Madagascar. Cœlopeltis, Macroprotodon, and Tarbophis are the northern outposts of an Afro-Indian group, although, with the exception of the third, exclusively confined to the circum-Mediterranean district. The genus Vipera is also represented in East Africa and in Southern Asia, but the species V. berus is essentially a northern type, extending to the highest latitude reached by any snake, and ranging all over Northern Asia to the Amur and Sachalien. The same species reaches the greatest altitude at which any snake has been observed on the northern side of the Alps—viz., 9,000 feet.

Of the twenty-eight species inhabiting Europe, only two are generally distributed: Tropidonotus natrix and Coronella austriaca. One is to be regarded as a northern form, although occurring locally in the south: Vipera berus. It is the reverse with Coluber longissimus. The others may be described as southern forms, two only as ranging from west to east: Zamenis gemonensis and Cœlopeltis monspessulana; one of more central habitat: Vipera ursinii. The remainder may be divided into two groups—those of more western, and those of more eastern distribution. To the first group belong Tropidonotus viperinus, Zamenis hippocrepis, Coluber scalaris, Coronella girondica, Macroprotodon cucullatus, Vipera aspis and Vipera latastii; to the second, Typhlops vermicularis, Eryx jaculus, Tropidonotus tessellatus, Zamenis dahlii, Coluber quatuorlineatus, dione, leopardinus, Contia modesta, Tarbophis fallax and iberus, Vipera renardi, ammodytes, lebetina, and Ancistrodon halys.

A remarkable fact in the distribution of European Snakes is the altitudinal range of Vipera berus, V. aspis, and V. ursinii. The first being the northernmost snake, generally distributed in Northern Europe and more locally in the south, should, one would expect, be a mountain form in the south. This is so in Switzerland, where it occurs chiefly between 2,500 and 9,000 feet, on the northern aspect of the Alps, whilst V. aspis lives at altitudes below 5,000 feet; but on the southern aspect of the same chain things are reversed, and V. berus is replaced by V. aspis, which reaches an altitude of 9,700 feet, whilst the former shows a tendency to abandon the mountains, and has established itself in a few localities in the plain of North Italy. Again, in France V. berus is the northern and V. aspis the southern species, yet the latter is the only one found on the French side of the Pyrenees (up to 7,250 feet), whilst the former reappears in North-Western Spain and Portugal at very low altitudes, even at sea-level. V. ursinii is a mountain form in Italy (Abruzzi), in France (Basses-Alpes), and in the Balkan Peninsula (up to 6,800 feet); but it is restricted to the plain in Lower Austria and Hungary, where V. berus occurs only in the mountains.

Only three species are entirely confined to Europe:

Coluber scalaris, Vipera ursinii, and V. aspis.

Of the species which range outside Europe, the following occur both in Western Asia and in North Africa:

Eryx jaculus, Tropidonotus natrix, Cœlopeltis monspessulana, Vipera lebetina.

In Western Asia and the North-East of Egypt:

Tropidonotus tessellatus, Zamenis dahlii.

In Western Asia:

Typhlops vermicularis, Zamenis gemonensis, Coluber quatuorlineatus, C. dione, C. longissimus, C. leopardinus, Coronella austriaca, Contia modesta, Tarbophis fallax, T. iberus, Vipera renardi, V. berus, V. ammodytes, Ancistrodon halys.

In North Africa:

Macroprotodon cucullatus.

In North-West Africa:

Tropidonotus viperinus, Zamenis hippocrepis, Coronella girondica, Vipera latastii.

The following lists will help to elucidate the distribution of the snakes in the different parts of Europe:

I. Scandinavia

1. Tropidonotus natrix (as far north as 65°).

2. Coronella austriaca (as far north as 63°).

3. Vipera berus (as far north as 67°).

II. Great Britain

1. Tropidonotus natrix (England and Wales, extreme south-east of Scotland).

2. Coronella austriaca (Surrey, Berkshire, Hampshire, and Dorsetshire).

3. Vipera berus.

III. Belgium and Holland

1. Tropidonotus natrix.

2. Coronella austriaca.

3. Vipera berus.

IV. Germany and Denmark

1. Tropidonotus natrix.

2. Tropidonotus tessellatus (Middle Rhine and Moselle, Saxony).

3. Coluber longissimus (Denmark, Schlangenbad, Treves).

4. Coronella austriaca.

5. Vipera berus.

6. Vipera aspis (Black Forest, Lorraine).

V. France and Switzerland, exclusive of Ticino

1. Tropidonotus natrix.

2. Tropidonotus viperinus (as far north as South Brittany and Fontainebleau).

3. Zamenis gemonensis (south, locally as far north as the Sarthe and Aube).

4. Coluber longissimus (locally as far north as South Brittany, South Normandy, and Fontainebleau).

5. Coluber scalaris (Mediterranean Littoral).

6. Coronella austriaca.

7. Coronella girondica (south and west as far north as the Charente-Inférieure).

8. Cœlopeltis monspessulana (Mediterranean Littoral).

9. Vipera ursinii (Basses-Alpes).

10. Vipera berus (as far south as the Loire basin, the Central Plateau, and the Alps).

11. Vipera aspis (as far north as the Loire basin, Fontainebleau, and Lorraine).

VI. Spain and Portugal

1. Tropidonotus natrix.

2. Tropidonotus viperinus.

3. Zamenis gemonensis (Catalonia).

4. Zamenis hippocrepis (absent from the north).

5. Coluber longissimus (Andalucia).

6. Coluber scalaris.

7. Coronella austriaca (north and north-west).

8. Coronella girondica.

9. Cœlopeltis monspessulana.

10. Macroprotodon cucullatus (centre and south, Baleares).

11. Vipera berus (north-west).

12. Vipera aspis (Pyrenees).

13. Vipera latastii (absent from the north).

VII. Italy, with Ticino and Corsica

1. Tropidonotus natrix.

2. Tropidonotus tessellatus (as far south as Naples; absent from the islands).

3. Tropidonotus viperinus (Liguria, Piedmont, Ticino, Corsica, Sardinia, Sicily).

4. Zamenis gemonensis.

5. Zamenis hippocrepis (Sardinia).

6. Coluber quatuorlineatus (south and Sicily).

7. Coluber longissimus (absent from Corsica).

8. Coluber leopardinus (south and Sicily).

9. Coronella austriaca (absent from Corsica and Sardinia).

10. Coronella girondica (absent from Corsica and Sardinia).

11. Cœlopeltis monspessulana (Western Liguria, Sicily).

12. Vipera ursinii (Abruzzi).

13. Vipera berus (the Continental part only).

14. Vipera aspis (absent from Corsica and Sardinia).

15. Vipera ammodytes (Northern Venetia).

VIII. Austria-Hungary, without Balkan States

1. Tropidonotus natrix.

2. Tropidonotus tessellatus.

3. Zamenis gemonensis (South Tyrol, Littoral, South Hungary).

4. Coluber quatuorlineatus (Istria).

5. Coluber longissimus.

6. Coluber leopardinus (Istria).

7. Coronella austriaca.

8. Coronella girondica (South Tyrol).

9. Cœlopeltis monspessulana (Istria).

10. Tarbophis fallax (Istria).

11. Vipera ursinii (Lower Austria, Littoral, Hungary).

12. Vipera berus.

13. Vipera aspis (South Tyrol, Littoral).

14. Vipera ammodytes (South Tyrol, Styria, Carinthia, Carniola, Littoral, South Hungary).

IX. Balkan Peninsula and Archipelago

1. Typhlops vermicularis (Greece, Turkey, Bulgaria).

2. Eryx jaculus (Greece, Turkey, Roumania).

3. Tropidonotus natrix.

4. Tropidonotus tessellatus.

5. Zamenis gemonensis.

6. Zamenis dahlii (coast of the Adriatic, Greece).

7. Coluber quatuorlineatus.

8. Coluber longissimus.

9. Coluber leopardinus.

10. Coronella austriaca.

11. Cœlopeltis monspessulana (West Coast, Greece, and islands).

12. Tarbophis fallax (West Coast, Greece and islands, Constantinople).

13. Vipera ursinii (Bulgaria, Bosnia, Herzegovina, Montenegro).

14. Vipera berus (Bosnia, Herzegovina, Roumania).

15. Vipera aspis (Bosnia).

16. Vipera ammodytes.

17. Vipera lebetina (Cyclades).

X. Russia

1. Tropidonotus natrix (as far north as 60°).

2. Tropidonotus tessellatus (south).

3. Zamenis gemonensis (south).

4. Zamenis dahlii (Caucasus).

5. Coluber quatuorlineatus (south).

6. Coluber dione (south, between Volga and Ural).

7. Coluber longissimus (south, Poland).

8. Coluber leopardinus (Crimea).

9. Coronella austriaca (as far north as 57°).

10. Contia modesta (Caucasus).

11. Tarbophis iberus (Caucasus).

12. Vipera renardi (south).

13. Vipera berus (as far north as 64°).

14. Ancistrodon halys (south, between Volga and Ural).

Without attempting anything like a complete bibliography, we have compiled a list of faunistic works and papers dealing with the snakes of Europe:

Europe in General

Schreiber, E.: Herpetologia Europæa. Zweite Auflage, Jena, 1912, 8vo.

Steinheil, F.: Die Europaeischen Schlangen. Kupferdrucktafeln nach Photographien der lebenden Tiere. Jena, 1913, 4to. (in progress).

Great Britain

Bell, T.: A History of British Reptiles. 2nd edit., London, 1849, 8vo.

Cook, M. C.: Our Reptiles. London, 1865, 8vo.

Leighton, G.: The Life-History of British Serpents. Edinburgh and London, 1901, 8vo.

France

Gadeau de Kerville, H.: Faune de la Normandie. IV. Reptiles. Paris, 1897, 8vo.

Lataste, F.: Essai d’une Faune Herpétologique de la Gironde. Bordeaux, 1876, 8vo.

Martin, R., et Rollinat, R.: Vertébrés sauvages du Département de l’Indre. Paris, 1894, 8vo.

Switzerland

Fatio, V.: Faune des Vertébrés de la Suisse. III. Reptiles et Batraciens. Geneva and Basle, 1872, 8vo.

Spanish Peninsula

Boscá, E.: Catalogue des Reptiles et Amphibies de la Péninsule Ibérique et des Îles Baléares (Bull. Soc. Zool. France, 1880).

Italy

Bonaparte, C. L.: Iconografia della Fauna Italica. II. Anfibi. Rome, 1832-1841, fol.

Camerano, L.: Monografia degli Ofidi Italiani (Mem. Acc. Torin., [2] xxxix., 1888, and xli., 1891).

Germany

Dürigen, B.: Deutschlands Amphibien und Reptilien. Magdeburg, 1890-1897, 8vo.

Leydig, F.: Ueber die Einheimischen Schlangen (Abh. Senck. Ges., xiii., 1883).

Austrian Empire

Werner, F.: Die Reptilien und Amphibien Oesterreich-Ungarns und der Occupationsländer. Vienna, 1897, 8vo.

Greece

Bedriaga, J. de: Die Amphibien und Reptilien Griechenlands (Bull. Soc. Nat. Mosc., 1881).

Bory de St. Vincent, J. B.: Expédition Scientifique de Morée. Reptiles. Paris, 1832-1835, 4to., fol. atlas.

Bulgaria

Kowatcheff, W. T.: Herpetological Fauna of Bulgaria. Philippopolis, 1912, 8vo. [Bulgarian text.]

Roumania

Kiritzescu, C.: Contribution à la Faune Herpétologique de Roumanie. Sauriens et Ophidiens (Bull. Soc. Rom. Bucarest, x., 1901).

Russia

Nikolsky, A.: Herpetologia Rossica. St. Petersburg, 1905, 4to. [Russian text.]

Strauch, A.: Die Schlangen des Russischen Reichs. St. Petersburg, 1873, 4to.

CHAPTER XIII
SNAKES IN RELATION TO MAN

Under this head, the question of poisonous snakes naturally occupies the first place. In addition to what has been said above in Chapter VI., dealing with the anatomical and physiological aspects of the subject, we have to allude to the accidents caused by these dangerous reptiles, and the measures taken to combat them.

The enormous mortality for which snake-bite is responsible in India is well known. Statistics establish the fact that an average of 20,000 human lives are thus lost annually: 24,264 is the official return for 1911. In Australia, where highly poisonous snakes of various genera and species abound, the fatal cases are likewise very numerous, though less in proportion than in South America, and no doubt also in Africa. In the small island of Martinique, the Fer-de-Lance, Lachesis lanceolatus, causes every year the death of about 100 human creatures. Though numerous in species, the poisonous snakes of Ceylon cause a comparatively small mortality—200 per annum.

Modern research has resulted in the discovery of the only effective antidote for snake-venom intoxication: the serotherapic treatment. An animal that has been treated over a length of time with the venom of a poisonous snake, such as a Cobra, yields a serum which is antitoxic towards that venom; but the great difficulty resides in the specificity of the different poisons, which often renders the use of the serum ineffective in countries like India and Australia, where several kinds of poisonous snakes occur in the same district (see above, p. [67]). In India, where a special laboratory has been established for the supply of antivenine, at the Central Institute of Kasauli, it has been found impossible to obtain any venoms but those of the Cobra and Russell’s Viper in sufficient quantity to immunize animals, and thus produce the serum necessary for dealing with the bite of the King Cobra, the Krait, and the Echis Viper.

In Pondicherry the French Government places annually a sum of 200 rupees at the disposal of the director of the hospital for obtaining Cobra poison, the snakes, to be brought alive, being paid for to the natives at the rate of half a rupee to one rupee each, according to size and condition. Six hundred and fifty-three specimens were thus purchased in less than two years (1901-1903). The poison is utilized for the preparation of Calmette’s antivenine, which, as we have said above, is only effective against cobra poison, and, unfortunately, useless for the cure of bites from other species.

In Brazil, where the number of accidents is estimated at 19,200 per annum, and that of fatal cases at 4,800, over 2,000 snakes (Lachesis and Crotalus) are brought annually to the Serotherapic Institute of Batantan, in the province of S. Paolo, for the preparation of the antitoxic serum, which is given in exchange for the snakes. According to the latest report of the Institute (1911), two serums are distributed: the anti-crotaline (for Rattlesnake bite) and the anti-bothropine (for Lachesis bite); the third, the anti-elapine (for Coral-snake bite), is in course of preparation.

In many countries a premium has for years been paid for the heads of poisonous snakes, and has led to the destruction of enormous numbers of them, without, however, resulting in a very appreciable diminution of the dangerous reptiles. More than £12,000 has been spent for this purpose in India alone; the numbers destroyed in 1885 and 1886 throughout British India amount to 420,044 and 417,596 respectively. About forty years ago the Governor of St. Lucia offered a reward of 4d. for every Fer-de-Lance’s head. But the negroes caught them alive and bred families of snakes for the sake of the reward, and thereby made what was for them a little fortune, these snakes bringing forth up to sixty young at a birth. The reward had to be abolished very soon.

Now about the Vipers of Europe, the only really dangerous snakes of this part of the world.

Although the Adder, Vipera berus, is quite common in many parts of England and Scotland, accidents caused by its bite are rarely heard of, and cases of death are few and far between. It is not so, however, on the Continent, where the same species, and especially its close ally, the more southern V. aspis, are responsible for many fatalities, due no doubt to the more virulent action of the venom in a warmer climate.

In the French Departments Loire-Inférieure and Vendée, where these snakes are very plentiful, three or four cases of death are reported annually. From 1860 to 1868, 370 serious accidents to man have been carefully recorded, 53 ending in death, not only in the case of children, but also of adults of all ages, in 10 cases within one to twenty-four hours. In the Puy-de-Dôme cases of death are of frequent occurrence. In Germany and in Switzerland, 12 or 13 per cent. of the cases on record have ended fatally. Instances of death from the bite of the south-eastern V. ammodytes are also not infrequent. On the other hand, the bite of V. ursinii, which is but seldom inflicted, is not known to have ever resulted in death.

It must be borne in mind that accidents are much more frequent in districts where the poorer classes are in the habit of going about barefoot.

Anyhow, it is certain that Vipers are a serious danger in many parts of Europe, not only to man, but also to horses, cattle, and dogs. And it is not surprising that efforts have been made to reduce their numbers. The most efficacious means, besides the protection of certain animals and birds which feed on Vipers, appeared to be the institution of premiums to be paid for the heads of the dangerous snakes. By offering 21⁄2d. per head, 500,000 Vipers (V. aspis) were destroyed from 1864 to 1890 in three French departments, Haute-Saône, Doubs, and Jura, and in one district (Chaumont) of the Haute-Marne 57,045 were killed from 1856 to 1861; this gives an idea of the extraordinary abundance of these snakes in some parts of France. In the Puy-de-Dôme the premium was fixed for a time at 5d., and one man managed to destroy in the course of seven years 9,175 Vipers (V. berus and V. aspis). A woman in the Deux-Sèvres has made a living for many years by catching Vipers, the heads of which were paid to her at the rate of 5d. each. The average number of her captures amounted to 2,062 per annum (mostly V. aspis). Around Oesnitz in Saxony, 2,140 V. berus were killed in 1889, and 3,335 in 1890. In a single district in Southern Styria the heads of 4,197 V. berus and 7,381 V. ammodytes were sent in for the reward in the course of two years (1892, 1893).

In spite of all this effort, the institution of the bounty has not answered expectations, and, with the exception of a few districts, Vipers remain as plentiful as ever, showing what little man can do in altering the equilibrium of Nature, except by interfering with the natural conditions under which animals live. Cultivation of the ground or destruction by fire of the vegetation of the wilderness seems to be the only efficacious means of getting rid of so abundant and prolific a creature as the Viper.

A word may be said, however, in defence of Vipers: they do a great deal of good to agriculture by the destruction of small rodents, on which they feed chiefly, and whose multiplication they serve to keep in check. It must be pointed out that, with the exception of the species of Coluber and Zamenis, other European snakes are to be regarded as indirectly injurious to agriculture, feeding as they do mainly on lizards or frogs and toads, which, as insectivores, deserve to be protected.

Snakes are not of much economic value to man. Tanned skins of Boas and Pythons are utilized for making shoes and fancy articles, such as purses, pocket-books, blotters, etc., and the Siamese make the drum-heads of native drums out of the skins of Pythons and Acrochordus. To say nothing of savages, who seem to be partial to the flesh of large snakes, the peasantry in some parts of France do not disdain snakes as an article of food, the Grass-snake being occasionally served in village inns under the name of Anguilles de haies, or hedge-eels.

Viper fat has for a long time been in request as an ointment in the case of various affections, and much used by quack doctors in the preparation of their remedies. Some forty years ago a chemist in Challans (Vendée) collected Vipers (V. aspis) for medicinal purposes, and was able to send several thousands to Paris in the course of a few years, thus realizing a considerable sum of money, but the demand has gradually fallen off since.

Very frequent in the past, snake-worship is still prevalent in many parts of India, where the Cobra is held in great veneration, and is never willingly killed by the Hindoo. In pre-Buddhist days the gods were represented with a canopy of five or seven Cobras over them. The North African Cobra was sacred to the ancient Egyptians, and is profusely represented on the monuments and tombs; it was also an emblem of the physical sun, and, as a sign of royal power, along with the sun’s disc, formed part of the headdress of all solar deities. The Greeks and Romans also worshipped snakes, and the god of medicine is represented holding a snake, which is supposed to be Coluber longissimus, the so-called “Æsculapian snake”; the occurrence at the present day of certain common Italian species (Zamenis gemonensis, Coluber longissimus, Tropidonotus tessellatus) in isolated localities of Central Europe, formerly Roman settlements, has been attributed to their importation for use in the temples.

Snake-charmers have existed from the remotest antiquity, and are still to be found among all races of men, from the accomplished Indian juggler down to the more commonplace European snake-catcher, who boasts of his immunity, and of his art of attracting snakes by devices of which he has the secret. The Libyan Psillii of the ancient Romans have handed down their art to the present day, and their performances are to be witnessed in most of the towns of Egypt and Tunisia. But India above all lands is reputed for its snake-charmers, and the favourite species used by them is the Cobra, which, by the way in which it raises the anterior part of the body and expands the region behind the head, lends itself better than any other to the display. Constantly facing the man before him, and swaying the raised anterior part of the body, it seems to dance to the music performed by the snake-man, people believing it to be charmed by the sounds of the instrument. However, anyone sitting on the ground in front of a Cobra, and swaying the body from side to side as does the man, can obtain the same result without the aid of any sort of music.

The most puzzling thing about these performances is how the man can thus play with impunity with so deadly a snake. It is a mistake to think that the snake is rendered harmless through the poison fangs having been extracted, although this subterfuge is frequently resorted to by the less accomplished jugglers. The immunity of the snake-charmer is to be explained by the fact that the man has submitted himself to a series of successive and graduated inoculations of the venom, a process similar to vaccination, which renders his blood proof against the venom of the particular species of snake, and that one only, used for his performances.

Another deadly snake shown by the snake-charmers in North Africa is the Horned Viper, Cerastes cornutus. The presence of an erect spike above the eye is, however, not a constant character in this snake, and hornless specimens are made to look more formidable by spines of the hedgehog being inserted in the proper place; the illusion is such that even naturalists have been deceived by this trick.

Indian snake-charmers profess to have a belief in the efficacy of snake-stones, or bezoar stones, as a remedy to be applied on the part bitten by a poisonous snake, a belief shared by the natives of many tropical countries. These stones, extracted from various reptiles, birds, and mammals, are calcareous concretions from the stomach or bladder, sometimes composed of superphosphate of lime, sometimes of phosphate of ammonia or magnesia. The value of a bezoar stone being supposed to increase with its size, the larger are sold in India at very high prices.

In many places a popular belief prevails that such stones are found in the heads of snakes. Mr. J. A. Bucknill, now Attorney-General at Hong-Kong, who spent five years in Cyprus, has informed the author that the Viper of the latter island, Vipera lebetina, is commonly believed to contain a stone which, when applied to the bite of a poisonous snake, quickly nullifies the effect; it is also believed that, when this stone is allowed to stand in a glass of water and the water is drunk, it endows the drinker with surprising virility. Indeed, there was an action tried by the English judge at Larnaka in which the plaintiff claimed the return, or damages for the non-return, of one of these “Viper-stones” which he had lent for a monetary consideration to the defendant for the promotion of his manly vigour, and Mr. Bucknill’s recollection is that the plaintiff recovered £10 for the loss.

SYSTEMATIC ACCOUNT OF THE SNAKES OF EUROPE[[1]]