Venoms: Venomous Animals and Antivenomous Serum-therapeutics. A. Calmette
and the fæces, which are voided some days later, contain only a few osseous remains and a felt-like material composed of hair or feathers.
Scales.—The skin of snakes, which is very elastic and extensile, is covered with scales, small on the back, and in great transverse plates on the entire ventral surface.
Fig. 14.—Arrangement of the Scales of the Head in one of the Poisonous Colubridæ (Naja tripudians, OR Cobra-di-Capello). (After Sir Joseph Fayrer.)
The shape and dimensions of the scales of the head are highly characteristic in each species. It is therefore necessary to know their names and the arrangement that they exhibit: these details are shown with sufficient clearness in figs. 13 and 14.
Coloration.—The colouring exhibited by the scales of snakes is governed generally by the biological laws of mimicry. It is therefore not a character of specific value, and may be modified several times in the course of the existence of the same reptile, according to the surroundings in which it is obliged to live.
“Nature,” write Dumeril and Bibron, “seems to have caused the tints and colours of snakes to vary in accordance with their habits and modes of life. Generally speaking, the colours are greyish or dull in species that are wont to live among sand, or which bury themselves in loose earth, as also in those that lie in wait on the trunks or large boughs of trees; while these hues are of a bluish-green, resembling the tint of the leaves and young shoots of plants, in snakes that climb among bushes or balance themselves at the end of branches. It would be difficult to describe all the modifications revealed by a general study of the colours of their skins. Let us imagine all the effects of the decomposition of light, commencing with white and the purest black, and passing on to blue, yellow, and red; associating and mixing them together, and toning them down so as to produce all shades, such as those of green, of violet, with dull or brilliant tints more or less pronounced, and of iridescent or metallic reflections modified by spots, streaks, and straight, oblique, undulating, or transverse lines. Such is the range of colours to be found in the skin of snakes.”
This skin is covered by a thick epidermis, which is periodically detached in its entirety, most frequently in a single piece. Before effecting its moult, the reptile remains in a state of complete repose for several weeks, as if asleep, and does not eat. Its scales grow darker and its skin becomes wrinkled. Then one day its epidermis tears at the angle of the lips. The animal thereupon wakes up, rubs itself among stones or branches, divests itself entirely of its covering as though it were emerging from a sheath, and proceeds forthwith in quest of food.
The moult is repeated in this way three or four times every year.
CHAPTER II.
HABITS OF POISONOUS SNAKES. THEIR CAPTURE.
All poisonous snakes are carnivorous. They feed on small mammals (rats, mice), birds, batrachians, other reptiles or fish, which they kill by poisoning them by means of their fangs.
They almost always wait until their prey is dead before swallowing it.
Some of them are very fond of eggs, which they well know how to find in the nests of birds, and swallow whole.
When a poisonous snake wishes to seize its prey, or strike an enemy, it raises its head, and depresses the lower and elevates the upper jaw in such a way that the fangs are directed straight forward. Then, with the quickness of a spring when it is released, the reptile makes a sudden dart and strikes its victim. After inflicting the wound it draws back, doubles up its neck and head, and remains prepared to strike again.
So rapid is the action of the venom, that the wounded animal falls to the ground almost immediately; it is forthwith stricken with paralysis, and dies in a few moments. In most cases the snake holds it in its mouth until death ensues; the reptile then sets to work to swallow its victim, an operation which is always slow and painful.
In captivity poisonous snakes almost always refuse to take any food whatever. If it be desired to keep them for a long time, it is often necessary to resort to artificial feeding. For this purpose the snake is seized by the head by means of a strong pair of long forceps; it is then grasped by the neck with the left hand without squeezing too hard (fig. 15), taking care at the same time not to give the body a chance of coiling itself round anything. Next, one or more lumps of beef or horse-flesh are introduced into the jaws, and gently forced down deep into the œsophagus by means of a glass rod, which is polished in order not to injure the mucous membrane. The œsophagus is then gently massaged in a downward direction, in order to cause the bolus of food to descend into the stomach (fig. 16). This operation is repeated every fortnight.
Fig. 15.—Feeding a Poisonous Snake, First Stage.
Fig. 16.—Feeding a Poisonous Snake, Second Stage.
Fig. 17.—Catching a Cobra-di-Capello (Naja tripudians), First Stage. (At the French Settlement of Pondicherry, in India.)
In this way, at my laboratory, I have been able to preserve, in perfect condition for more than two years, Indian Cobras and Fers-de-lance from Martinique, taking care to keep them in a hothouse, at a temperature of about 82° to 86° F.
It is also very important to place inside the cases a vessel full of water, which should be frequently changed, for almost all snakes drink often and like to bathe for whole days at a time.
Fig. 18.—Catching a Cobra-di-Capello (Naja tripudians), Second Stage. (At the French Settlement of Pondicherry, in India.)
Within their reach should be placed in addition branches and rockwork, against which they rub at the moulting times, in order periodically to rid themselves of their scarf-skin.
While moulting, snakes must neither be touched nor fed, since to force them to take food at such a time would be fatal.
Snake-catching.—The capture of poisonous snakes, in order to keep them alive, can only be performed without danger by skilful persons, who are possessed of much coolness.
The best way of securing them is suddenly to pin the neck to the ground by means of a stick held horizontally, or a small two-pronged fork of wood or metal (fig. 17).
The stick is rolled along until close to the occiput (fig. 18). The animal can then be seized with the hand immediately behind the head, in such a way that it is impossible for it to turn and bite. It is then put into a wire cage, provided with a small movable trapdoor, with the fastening on the outside.
In this way poisonous snakes can be sent to a distance, and left without food for one or even two months, provided that they be kept in a place which is somewhat moist and sufficiently warm.
Fig. 19 shows how captured cobras are carried in India, in the environs of Pondicherry. They are enclosed in earthern chatties, or in baskets of plaited bamboo, which are provided with covers, and are very convenient for carrying snakes short distances.
Fig. 19.—Hindu carrying Two Captured Cobras in “Chatties.”
CHAPTER III.
DESCRIPTION OF THE PRINCIPAL SPECIES OF POISONOUS SNAKES.