C.—Arthropods.
(a) Araneida (Spiders).
Almost all Arachnids possess poison-glands, which are connected, in some cases with the buccal apparatus, in others with a special inoculatory organ situated at the posterior extremity of the body. The spiders and scorpions belong to this group, and their venom is particularly active.
On each side of the mouth of spiders is found an appendage ending in a fang (chelicera), at the extremity of which opens the excretory duct of a more or less developed poison-gland. The venom produced by these glands is instantly fatal to all small animals upon which spiders feed. In man and large mammals their bite produces sensations of pain accompanied by swelling and muscular contractions as though caused by localised tetanus.
The venom of certain species of spiders sometimes causes very serious and even fatal results. Latrodectus malmignattus (the malmignatte of the South of France and Italy), and especially Latrodectus mactans, of Chile ([fig. 96]), are greatly dreaded.[111] The area of distribution of the latter includes the whole of Tropical and Sub-tropical America. It is said that it frequently causes the death of milch cows, and that in man its bite produces tetanic effects, which last for several days, but are in most cases amenable to treatment.
Fig. 96.—Lactrodectus mactans (formidabilis olim).
1, Female, twice natural size; 1a, its eyes, greatly enlarged.
Another dangerous spider is the Katipo (Latrodectus scelio), of New Zealand. This creature is confined to the sea-shore, and the natives are often bitten when collecting shell-fish or sea-weed. The Maoris are so much afraid of the bite of the Katipo that, when one of them has been bitten in his hut, and the animal cannot be found, they do not hesitate to burn the dwelling to the ground. Moreover, they are convinced that the death of the spider is absolutely necessary for the recovery of the patient.[112]
Kobert[113] has made an experimental study of the venom of species of Latrodectus and Epeira. That of Latrodectus erebus (the Karakurte of South Russia) is particularly toxic.
If a dry extract of these spiders be prepared and injected into the veins of dogs or cats, it is found that a few milligrammes per kilogramme are sufficient to cause death, with phenomena of dyspnœa, convulsions, and progressive paralysis of respiration and the heart. Rabbits, rats, birds, frogs, and leeches are also sensitive to this poison, though the hedgehog is almost refractory. The young spiders, and even the eggs, are more toxic than the adults.
Spider-venom is destroyed by heating for forty minutes at + 70° C., and is precipitated by alcohol. When absorbed by ingestion it has no effect: it is hæmolytic and coagulates blood.
The study of arachnolysin by Ehrlich’s methods has been undertaken afresh by Hans Sachs,[114] who has shown that rat’s and rabbit’s blood are most rapidly dissolved. Twenty-eight milligrammes of extract of Epeira are capable of completely dissolving 0·05 c.c. of blood.
By immunising guinea-pigs and rabbits, Sachs succeeded in obtaining a strongly antitoxic serum, which entirely prevents the hæmolysis of the sensitive red corpuscles.
(b) Scorpionidea (Scorpions).
The poison-apparatus of the scorpion is constituted by the last abdominal segment (telson), which is swollen and globular, and terminated by a hard, curved spine, with a very sharp point, near which can be distinguished, under the lens, two small oval orifices by which the poison is enabled to escape ([fig. 97]).
The poison-glands are two in number, symmetrically placed in cavities, each of which is completely filled by the gland. They are separated from each other by a muscular septum formed of striated fibres inserted in the chitinous skeleton; by the contraction of this septum the animal is enabled to eject its venom.
Fig. 97.—Scorpio occitanus. (After Joyeux-Laffuie.)
1, Scorpion seizing a spider, and piercing it with its sting (natural size); 2, extremity of the abdomen (telson) enlarged, showing the poison-apparatus; 3, poison-apparatus detached from the abdomen, showing an isolated poison-gland.
The scorpion never stings backwards, but always in front of itself. It delivers stabs with its sting in two distinct ways. For the purpose of defending itself from attack it elevates its abdomen into a bow, and then regains its former position by suddenly unbending it. To strike an animal, such as a spider, which serves it for food, the scorpion seizes it with its pincers and holds it as in a vice. Then it raises its abdomen, brings the end of it close to its captive, and, with a lever-like movement, drives the sting into its body. The victim immediately becomes paralysed and motionless.[115]
The poison-glands of a Scorpio occitanus from the South of France contain about 1 to 10 centigrammes of a toxic liquid, capable of furnishing 10 to 15 per cent. of dry extract. This liquid is decidedly acid; it reddens litmus paper and is miscible with water.
Its physiological effects are especially intense in the case of the arthropods upon which the scorpion habitually feeds, and in that of vertebrates in general. Batrachians, fishes, birds, and mammals are extremely susceptible to this poison. Half a milligramme of dry extract injected subcutaneously is sufficient to kill a guinea-pig, and 1 milligramme is lethal to the rabbit.
In poisoned animals there is first observed a period of violent excitement, accompanied by very acute pains; these are followed by muscular contractions, and finally by paralysis of the respiratory muscles, as in the case of intoxication by cobra-venom.
The effects of scorpion-poison, which clearly indicate the presence of a neurotoxin, have been very well described by Valentin,[116] Paul Bert[117] and Joyeux-Laffuie. Kyes[118] has prepared a lecithide from scorpion-venom, which hæmolyses red corpuscles as do the lecithides of cobra-venom, and I myself[119] have established the fact that the antivenomous serum of a horse vaccinated against cobra-venom effectively protects mice and guinea-pigs against intoxication by the venom of Scorpio occitanus; this has been verified by Metchnikoff. There is, therefore, a close affinity between this venom and that of Colubrine snakes.
On the other hand, it has been shown by the investigations of C. Nicolle and G. Catouillard that the same antivenomous serum has no effect upon the much weaker venom of the scorpion of Tunis (Heterometrus maurus), which, in the case of man and mammals in general, scarcely does more than produce a transient œdema at the point of inoculation.
The venom of Heterometrus maurus is, however, toxic enough to the sparrow. When one of these little birds is inoculated in the pectoral muscles with the contents of the poison-glands of a single scorpion belonging to this species, the following symptoms are observed: Immediate rigidity, doubtless connected with the pain, then, after a few seconds, depression and relaxation of the muscles. The bird remains upright, but its body sinks down more and more until it comes into contact with the ground; if on a perch, it soon becomes unsteady and drops off. There is dyspnœa, which any effort increases, and death supervenes suddenly; all at once the sparrow falls on its side, stiffens, sometimes has a few convulsions, and then finally becomes still. The time occupied by these phenomena is always short, although it varies from two minutes to half an hour.
Scorpion-venom is a strong irritant to the mucous membranes. When dropped into the eye of a rabbit it produces acute ophthalmia.
It has often been asserted that scorpions kill themselves with their own venom if enclosed in a circle of fire. This is an absolute myth, for it is easy to prove by experiment, as was done by Bourne at Madras,[120] that these animals cannot be intoxicated by their own poisonous secretion, nor by that of other individuals of the same species. Moreover, it has been established by Metchnikoff,[121] in very definite fashion, that the blood of the scorpion is antitoxic. If 0·1 c.c. of this blood be added to a dose of venom lethal to mice in half an hour, a mouse injected with this mixture resists indefinitely. This antitoxic power is exhibited both by Scorpio afer and the Algerian Androctonus.
(c) Myriopods.
It has been shown by Phisalix and Bertrand that certain species of Myriopods, including those of the genus Julus (Order Chilognatha, e.g., Julus terrestris), secrete throughout the entire extent of their body a volatile venom, which these authors compared to quinone.
The species of the genus Scolopendra (Order Chilopoda; Scolopendra cingulata, found in the South of France, Spain and Italy; S. gigantea and other forms, common in Africa, India, Indo-China and Equatorial America), have the second pair of post maxillary appendages transformed into formidable poison-claws, with which they can inflict bites which are very painful to human beings.
Fig. 98.—Scolopendra morsitans (S. Europe).
(After Claus.)
The tropical species may attain a length of 10 or even 15 cm. Their bodies are composed of 21 segments, each provided with a pair of jointed legs. They live in shady places, such as woods, hidden under stones, dead leaves, or the bark of old trees. They feed upon small insects, spiders, and larvæ, which they kill with their venom. The latter is secreted by a racemose gland situated at the base of the poison-claws; it escapes by a duct which opens at the apex.
This venom, the physiological study of which was commenced by Dubosq, is an acid, opalescent liquid, hardly miscible with water.
More complete experiments on this subject have been made by A. Briot,[122] who prepared a solution by sectioning the labium and poison-claws, and crushing the whole in physiological salt solution. When injected intravenously into rabbits, it produces immediate paralysis, with coagulation of the blood; subcutaneously it leads to the formation of enormous abscesses, with necrosis of the tissues. Small animals, such as spiders, species of Scutigera, beetles, &c., are very sensitive to it.
The bite of Scolopendridæ is very painful to human beings. In the Tropics such bites often cause somewhat serious results: insomnia, accelerated and intermittent pulse, and local œdema, which usually disappears after twenty-four hours. Well-authenticated fatal accidents have never been recorded (Bachelier,[123] Saulie[124]).
(d) Insects.
A very large number of insects produce acrid or irritant secretions, which serve them as a means of defence, but cannot be considered as true venoms; the species of Meloë (oil-beetles) and Cantharis (blister-beetles), are the most remarkable in this respect.
The Order Hymenoptera is the only one that includes a multitude of species really provided with poison-glands and an inoculatory apparatus.
Fig. 99.—Poison-apparatus of the Bee.
gl.ac, Acid gland and its two branches; V, poison-sac; gl.al, alkaline gland; gor, gorget.
(After Carlet: figure borrowed from Hommel.)
The poison-organs, which have been well studied, especially by Leuckart,[125] Leydig,[126] Carlet,[127] and more especially by L. Bordas,[128] Janet,[129] and Seurat,[130] always include two and sometimes three kinds of glands: the acid gland, the alkaline gland or gland of Dufour, and the accessory poison-gland ([fig. 99]).
The acid gland comprises a glandular portion (which sometimes takes the shape of a long flexuous tube, always bifid at its extremity, sometimes that of two tubes, simple or ramified, or again is composed of a bundle of cylindrical, simple or multifid canals), a poison-sac or reservoir, ovoid or spherical in shape, and an excretory duct, which is usually short.
The alkaline gland, or gland of Dufour, exists in all Hymenoptera, and presents the appearance of an irregular tube, with a striated surface and a spherical or conical upper extremity. Its excretory duct opens, beside that of the acid gland, at the enlarged base of the gorget of the sting ([fig. 100]).
Fig. 100.—Interior of the Gorget of the Bee, seen from its Posterior Aspect.
cv, Poison chamber; gor, gorget; st, stylet; ca, piston. Between the two stylets is seen the cleft fa, by which the air is able to enter into the air-chamber cai.
(After Carlet: figure borrowed from Hommel.)
The accessory poison-gland, which is lanceolate or ovoid in shape, consists of a small, granular mass, the extremely narrow excretory duct of which opens at almost the same point as that of the alkaline gland. It does not exist in all Hymenoptera.
The stings of hive bees (Apis mellifica), wasps (Vespa vulgaris), violet carpenter bees (Xylocopa violacea), and humble bees (Bombus lapidarius) cause considerable discomfort. The venom of the carpenter bee, which is of some strength, has been studied by P. Bert, and I have myself made experiments with that of the hive bee (A. mellifica). The venom extracted from a couple of bees, by crushing the posterior extremity of the body in 1 c.c. of water, is sufficient to kill a mouse or a sparrow.
Death supervenes in a few minutes, from respiratory asphyxia, as in the case of intoxication by the venom of Colubrine snakes (Cobra). In the blood-vessels and in the heart the blood is black and remains fluid. It therefore appears that this venom contains a very active neurotoxin.
The phenomena of intoxication caused by the venom of these insects are, as a rule, slight, being limited to an acute pain, accompanied by a zone of œdema and burning itching. Sometimes however, when the stings are in the eyelids, lips, or tongue, they produce alarming and even fatal results, as shown by the following incident:—
On September 26, 1890, a young girl of Ville-d’Avray was eating grapes in the woods of Fausse-Repose, when she inadvertently swallowed a wasp. The unfortunate girl was stung in the back of the throat, and the wound became so rapidly inflamed that, in spite of the attentions of a doctor, she died in an hour from suffocation, in the arms of her friends.
Phisalix[131] has studied the physiological action of bee-venom on sparrows inoculated either by the sting of the insect, or with an aqueous solution obtained by crushing the glands. In both cases a local effect, paralysis of the part inoculated, is first produced; this is followed by convulsions, which may last for several hours; the final stage is marked by coma and respiratory trouble, which ends in death.
After being heated for fifteen minutes at 100° C. the venom has no further local action; the general phenomena are merely diminished. If heated at 100° C. for thirty minutes, the venom ceases to cause convulsions, but remains stupefactive. Exposure for fifteen minutes to a temperature of 150° C. renders it completely inert.
This venom therefore comprises: (1) A phlogogenic substance, destroyed by ebullition, contained in the acid gland of the bee; (2) a poison causing convulsions, which does not resist a temperature of 100° C., if prolonged, and is probably produced by the alkaline gland; (3) a stupefactive poison, which is secreted by the acid gland, and is not entirely destroyed until a temperature of 150° C. is reached.
The poison-glands can easily be extracted by gently pulling at the stings of bees anæsthetised by chloroform.
The eggs of bees, like those of the toad and the viper, contain the specific venom. The amount, however, is small, since in order to produce lethal results in the sparrow it was found necessary to inoculate an emulsion obtained by crushing 926 eggs.
Phisalix[132] makes the approximate calculation that, in the egg the weight of the toxic substances amounts to the one hundred and fiftieth part of the whole. Their effects are similar to those produced by the venom itself, but the convulsions are not so severe. The predominant poison in the egg appears to be that causing paralysis.
I have easily succeeded in vaccinating mice against doses of bee-venom certainly lethal, by repeatedly inoculating them with very small doses. Moreover, we find the same thing in the case of human beings, for we know that those who are in the habit of handling hives become quite accustomed to bee-stings, and finally feel not the slightest effect from them.
It has been shown by J. Morgenroth and U. Carpi,[133] in a paper recently published, that the venom of bees, like that of the scorpion, possesses the property of hæmolysing the red corpuscles of several species of animals (the rabbit, guinea-pig, and goat), and that it is capable of combining with the lecithin to form a lecithide analogous to cobra-lecithide, the curious properties of which we have studied in detail.
This lecithide of bee-venom is from 200 to 500 times more hæmolysing than the venom itself, and resists ebullition like that of the cobra. In order to isolate it Morgenroth and Carpi employed the method recommended by P. Kyes: 1½ c.c. of a solution of pure venom is mixed with 1½ c.c. of a 5 per cent. solution of lecithin in methylic alcohol. After being kept for twenty-four hours at 37° C., 22 c.c. of absolute alcohol are added; the liquid is decanted, and the clear filtrate is mixed with 150 c.c. of ether. There is slowly formed a somewhat copious flocculent deposit, which is collected on a filter, washed several times with ether, and finally dried. The lecithide that remains on the filter dissolves completely in physiological salt solution.
It must be remarked that bee-venom, without the addition of lecithin, gives a scanty precipitate with ether. This precipitate, dissolved in physiological salt solution, possesses no hæmolysing power. The lecithide, on the contrary, dissolves red corpuscles almost instantaneously.
Normal horse-serum considerably inhibits hæmolysis by bee-venom + lecithin. This protective action of normal serums has already been observed by Langer; it is perhaps attributable to the cholesterin that they contain.
Among other Hymenoptera capable of inflicting very severe stings may be mentioned the species of Polistes and certain Pompilids, especially a species of Pompilus found in Natal, the painful stings of which have sometimes been experienced and described by travellers (P. Fabre, of Commentry).[134]
In the family Crabronidæ the females are provided with a sting and venom, which usually has little effect upon man, but is toxic to other insects. Thus, Cerceris bupresticida is remarkable for the stupefying effect of its venom upon the Buprestidæ destined for the food of its larvæ. It stings the beetles between the first and second segments of the thorax, with the result that the victim is paralysed, though in other respects its bodily functions appear to continue; in fact, its intestine is seen to empty itself at long intervals. These effects are attributed by Mons. J. H. Fabre, of Avignon, to the direct action of the venom upon the ganglia of the thoracic nervous system.
Instances of Hymenoptera belonging to the tribe Entomophaga actually depositing their eggs beneath the skin of man are mentioned by Raphaël Blanchard.[135]
According to P. Fabre, the best treatment for wasp- or bee-stings would appear to consist in the application of strong saline solution, or a liniment of ammonia and olive oil. For my own part, I have tried hypochlorite of lime, in a 1 in 60 solution, or eau de Javel diluted to 1 per cent., and have always obtained such excellent results from these remedies that I do not hesitate to advise their use.