Snakes: Curiosities and Wonders of Serpent Life

by Catherine Cooper Hopley

A few more words descriptive of the external aspect of the Viperidæ may summarize what has already been said of them. Schlegel suggests that their ‘noxious character is expressed in all their parts.’ With the exception of brilliant colouring, this may be accepted as a rule. The broad, flat, angular head, rendering the ‘neck’ thin and conspicuous, has gained for many of them the generic, sometimes specific name of Trigonocephalus. From their deadly qualities, Clotho, Severa Atrox, Lachesis, and Atropos are among their names; while caudalis and brachyura describe the short, thin tail as opposed to the long and tapering tails of most colubrines. The true vipers—those that have not the nasal fosse—belong particularly to Africa, the Crotalidæ proper to America, the chief distinction being that the Crotalidæ have and the Viperidæ have not the ‘pit’ (see p. 277), of which more in the next chapter. The rigid, lanceolate scales covering the head are another viperine characteristic; also thick, heavy bodies, tapering at each end, and rough, carinated scales. They inhabit for the most part dry, arid deserts and sandy uncultivated places of the Old World, Africa being their most congenial habitat. The coloured viper and young one convey a good idea of their general aspect.

Ophiologists do not agree in the arrangement of genera and species, on account of the forms running so much into each other. Gray gives nine genera and twenty species; Wallace, three genera and twenty-two species; and Dumeril, six genera and seventeen species. The Death adder of Australia (p. 172) is a heterogeneous species. Its aspect is viperine, yet it has not viperine fangs, and does not therefore belong to this chapter. Schlegel thinks it ought not to be separated from the true vipers, but Krefft does not state positively that it is viviparous, so it is altogether anomalous.

The researches of Dr. Weir Mitchel of Philadelphia have been of great value to ophiologists. For two whole years he gave the best portion of his time to the study of rattlesnakes, having a number of them under constant observation. An exhaustive paper by him was published in the Smithsonian Contributions, Washington, D.C., in 1860, giving details of experiments with the venom and the treatments adopted. But of especial interest here are his observations on the fangs and their volitional action, it having previously been supposed that the mere opening of the mouth brought the fangs into position, which is not the case. As the Crotalus can move each side of its mouth independently, so it can use one or both fangs. ‘When the mouth is opened widely, it still has perfect control over the fang, raising or depressing it at will.’ Dr. Mitchel saw that though both fangs were present, both were not always used. When a viperine snake yawns extensively, as it so often does, you may sometimes perceive the fangs partially erected or entirely so, or the ‘vibratile motion’ in them observed by Fayrer. When the snake is angry, this vibratile action is much like that of a cat gnashing the teeth; but when only in a yawn, the partial and unequal erection of one or both fangs has the appearance of being involuntary. In this I speak from observation. The effect is similar to that seen about a person’s mouth in trying to suppress a yawn—a sort of convulsive, nervous twitching. Whatever the cause, you perceive the fangs moving, but not moving always in accord.

The shedding or replacement of the fangs is, Dr. Mitchel thinks, a regular process, as in the teeth of some fishes, though not regular as to time. Sometimes, but not always, they are shed with the casting of the cuticle. He ‘cannot suppose that the almost mature secondaries are awaiting an accident;’ which agrees precisely with the opinions of Dr. Edward Nicholson and other physiologists quoted in the last chapter: ‘A crop of young teeth’ (or of fangs) ‘work their way into the intervals of the old teeth, and gradually expel these latter.’ When lost by accident or by violence, therefore, the process of replacement is slower, as we can readily conceive, the ‘secondary’ next in turn not being as yet ready for duty.

Though the American scientific journals devoted to zoology are rich in ophidian literature, there are few available to English students; and I regret I am unable to ascertain from across the Atlantic the latest researches and conclusions regarding this and several other correlative points. To Professor Martin Duncan I am indebted for the loan of a volume which forms one of the ‘Bulletins’ of the United States Geological Surveys, containing a valuable ‘Report’ on the Crotalus by Dr. Elliot Coues, of the United States army, late surgeon and naturalist to the United States Northern Boundary Commission, 1878.

It is these frequent Exploring Expeditions of America that have done so much to enrich science in all its branches; as to them are appointed efficient geologists, botanists, naturalists, and other scientists, who send in their ‘Reports’ to Government, to be soon reproduced in the form of large, handsomely-illustrated volumes. Copies of these (often consisting of ten to eighteen thick quartos) are presented to the members of Congress, governors of States, and to many others in office, also to literary institutions. You may have access to them in almost every large town in America; and there is no information connected with the history and natural productions of the nation (including the aborigines) that cannot be found in their pages. And as our Transatlantic cousins are always exploring some new territory, and have still untold square miles of mountain and valley to explore, their scientific ‘Reports’ in huge quarto tomes can be more easily imagined than counted.

This little digression from the viperine fangs is by way of introducing Dr. Elliot Coues. The volume in question was not forthcoming at the British Museum, therefore I ventured to trouble Professor Duncan with some inquiries, which were kindly responded to by the sight of the work itself.

There is in Dr. Coues’ paper a good deal of what has been here already described; but there is also so much that is of additional interest, that for the benefit of those students who are not within reach of the British Museum (where, no doubt, the fast arriving quartos will get catalogued in due time), I will transcribe from the text some of the passages as relating to viperine fangs generally.

‘The active instruments are a pair of fangs.’ ... They are ‘somewhat conical and scythe shaped, with an extremely fine point; the convexity looks forward, the front downward and backward’ (referring to the slight double curve in the Crotalus fang as shown in the illustration, p. 360). They are hollow by folding, ‘till they meet, converting an exterior surface first into a groove, finally into a tube.’ ... The fang is ‘moveable, and was formerly supposed to be hinged in its socket. But it is firmly socketed, and the maxillary itself moves, which rocks to and fro by a singular contrivance. The maxillary is a small, stout, triangular bone, moveably articulated above with a smaller bone, the lachrymal, which is itself hinged upon the frontal.... This forward impulse of the palatal and pterygoid is communicated to the maxillary, against which they abut, causing the latter to rotate upon the lachrymal. In this rocking forward of the maxillary, the socket of the fang, and with it the tooth itself, rotates in such a manner that the apex of the tooth describes the arc of a circle, and finally points downward instead of backward. This protrusion of the fang is not an automatic motion, consequent upon the mere opening of the mouth, as formerly supposed, but a volitional act, as the reverse motion, viz. the folding back of the fang, also is; so that in simply feeding the fangs are not erected.’ (But I think I may affirm positively that sometimes the vipers do use their fangs in feeding. When they open their mouths—or rather the jaws alternately very wide—I have seen first one and then the other fang occasionally engaged in the food and again disengaged unsheathed. On other occasions the fangs have been folded. In some large African vipers, the ‘River Jack’ and others that were in the Society’s Gardens a few years ago, I was able to observe this easily.)

The fang is folded back ‘with an action comparable to the shutting of the blade of a pocket-knife; ... one set of muscles prepares the fangs for action, the other set stows them away when not wanted.... The fangs are further protected by a contrivance for sheathing them, like a sword in its scabbard. A fold of mucous membrane envelops the tooth like a hood.... The erection causes the sheath to slip, like the finger of a glove, and gather in folds round its base.... It can be examined without dissection.’ (And with the naked eye in a large viper, even during life, you may sometimes perceive this sheath or hood half off.) ‘Each developing fang is enclosed in a separate capsule,’ says Dr. Mitchel, which is just what I thought I saw in ‘grovelling’ up the poor Bushmaster’s reserve fangs. There was an immense deal of loose skin to remove, which under skilful manipulation would doubtless have presented the form of sheaths of various sizes. At last I came to a great deep cavity as big as a bean or a hazel nut, and this I left neat and uninjured for some one else to explore. It might have been the poison gland! The young Jararaca’s mouth is too small to reveal its mysteries.