George Albert Boulenger

“ 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. ”

“ 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. ”

“ 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 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 ”

“ The sense of sight appears to be better developed than in any other European snake. The food consists chiefly of mammals, even large rats and young rabbits, birds such as chickens, partridges, and quails, lizards, and other snakes, which, if of considerable size, are not swallowed until paralyzed or killed by the effect of the poison. In Eastern 212 Europe, Vipera ammodytes is said to be the principal enemy of Cœlopeltis, and the two snakes are consequently seldom found together in the same locality. ”

“ 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. ”

“ 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 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. ”

“ The food consists mostly of lizards, occasionally of slow-worms or small snakes, more rarely of voles or mice, even shrews, which are seized, constrictor-like, and crushed by the coils of the body. O. von Tomasini has observed one swallowing a Coluber longissimus as large as itself.
In Central Europe this snake becomes active towards the end of March or beginning of April, and retires in September or October. It does well in captivity, and becomes very tame. It is one of the most intelligent of snakes, second to none in educability; 202 it can be trained to feed in the hand of its master. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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 141 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. ”

“ To his utter surprise, some of them actually made for him, swimming along rapidly with the head erect, about 6 inches above the water, and darting forwards with widely opened jaws; but they did not bite. According to Professor Kathariner, this snake when caught has been observed to sham death, lying rigid and motionless, with open gape. Some specimens do well in captivity, and are known to have lived for many years; others refuse all food and die of starvation. After a time they become tolerably tame, and cease to produce the offensive odour when handled. ”

“ 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. ”

“ 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. ”

“ Black specimens occur, more or less frequently, all over the habitat of this species, and are often referred to as V. prester, Linnæus. A distinction has to be made between individuals which are black through darkening of the ground colour, and such as are thus coloured through expansion and confluence of the markings. The latter are males, and among them we may find intermediate stages showing how this melanism is brought about; in one case the black of the back is separated from the black of the sides by a narrow light brown wavy stripe, the remains of the ground colour. ”

“ 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 ”

“ 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. ”

“ 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. ”

“ 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 38 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. ”

“ 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. ”

“ 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 104 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. ”

“ 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 9 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. ”

“ 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 134 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 ”

“ The food consists of small mammals and birds, and also of lizards. V. ammodytes does much better in captivity than its European congeners, and takes food more readily.
The hissing is louder than in V. berus and V. aspis, and it is often produced, on the approach of man, by specimens lying in such perfect concealment that their presence would not otherwise be suspected; this habit, like the rattling of the Crotalus, is evidently detrimental to the species in its relation to man. ”

“ 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 70 results unless a remedy be speedily applied. ”

“ 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. ”

“ 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. ”

“ 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. ”