seconds. This air, when it has performed its office, and has been deprived of its oxygen, is expelled in the same manner, but by an inverse mechanism, which is entirely due to the action of the muscles which tend to approximate the ribs to each other. When it is expelled rather briskly, a sort of vibration or hissing is heard."

The learned zoologists just cited have given some interesting illustrations of the absorbent powers of the intestines of serpents. Their fæcal evacuations afford a singular proof of this; for they present, as it were, the dry extract of the animal swallowed, in an entire state; the parts that could not be dissolved remaining unaltered, and absolutely in the same situation that they occupied in the carcase of the animal before it had passed through the whole length of the digestive tube. If, for instance, a rat has undergone this process, one may recognise in the dry and shapeless mass, the place occupied by the muzzle of the animal, the long whiskers of its cheeks, the down which covered the delicate cartilages of its ears, the hairs of various lengths and colours which correspond with those of the back, the belly, and above all, the tail; and finally, even the claws, which remain in their pristine state of integrity. All that was flesh or soft matter in the body has been completely absorbed; the earthy salt, nevertheless, which gave, by means of its union with the gelatine, consistence to the bones, still indicates by its presence, and especially by its colour, the place they occupied. Dissolution, compression, and absorption, have done their work upon this desiccated mass, which still, however, contains the elements of nourish

ment for the larvæ of the insects of the Family Dermestidæ.

When irritated or alarmed, some of the Serpents (the non-venomous ones, at least) have recourse to two very distinct actions, both of which seem to be means of defence. The first is the production of the shrill sound already alluded to, called hissing, by the forcible ejection of air from the narrow glottis. This sound, though so familiarly spoken of as to have become almost proverbial, we cannot help thinking, is uttered rather infrequently; as we have seen species of Colubrida and Boadæ excited to rage, but do not remember ever to have heard the " hissing" in question. MM. Duméril and Bibron also state that they never could hear more than a sort of blowing (soufflement), such as would result from the rapid issue of a current of air through a simple pipe, a quill, for instance. The other defence is much more certain, and less likely to be overlooked. It consists in the diffusion of a fetid, sickening odour, so nauseous as to be overpowering. It proceeds from certain glands situated near the orifice of the body. We have remarked in the Boa, that the urine, which is discharged in the form of a butyraceous pulp, like moist plaster of Paris, has the same fetor.

White of Selborne gives the weight of his testimony to both of these modes of defence. "I wish I had not forgot to mention the faculty that snakes have of stinking se defendendo. I knew a gentleman who kept a tame snake, which was in its person as sweet as any animal while in good humour and unalarmed; but as soon as any stranger, or a dog, or a cat, came in, it fell to

hissing, and filled the room with such nauseous effluvia, as rendered it hardly supportable."*

The eggs of serpents are enclosed in a calcareous covering, which is not hard and shelly, but tough, somewhat resembling kid-leather, or wet parchment. They are often numerous, and are deposited together, and connected by a sort of glutinous matter. Holes in the earth, in dunghills, or in heaps of decaying vegetable matter, are situations frequently chosen for their reception; and here they are left to be hatched by the heat of the weather, or by that which is developed in the putrefactive fermentation of the surrounding mass. The venomous species, as far as we are acquainted with their habits, are ovo-viviparous, the membrane of the egg being ruptured either before or during parturition.

We have said that the instruments of progressive motion in the Serpent tribes are the multitudinous ribs. The vertebræ of the spine admit of excessive flexibility, and the ribs are jointed upon them in a manner which allows the latter an extent of motion unusually great. The mode in which a Serpent proceeds will be understood from the following observations, the reader bearing in mind that the whole under surface of the body is shod, as it were, with broad plates, or scuta, the hinder margins of which are free. "When the Snake," says Sir Everard Home, begins to put itself in motion, the ribs of the opposite sides are drawn apart from each other, and the small cartilages at the end of them are bent upon the upper surfaces of the abdominal scuta, on which the ends of the ribs rest; and * Letter XXV. (1st series.)

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as the ribs move in pairs, the scutum under each pair is carried along with it. This scutum, by its posterior edge, lays hold of the ground and becomes a fixed point from whence to set out anew. This motion is beautifully seen when a snake is climbing over an angle to get upon a flat surface. When the animal is moving, it alters its shape, from a circular or oval form to something approaching a triangle, of which the surface on the

ground forms the base. The Coluber and Boa having large abdominal scuta, which may be considered as hoofs or shoes, are the best fitted for

this kind of progressive motion.”

"An

observation of Sir Joseph Banks during the exhibition of a Coluber of unusual size first led to this discovery. While it was moving briskly along the carpet, he said he thought he saw the ribs come forward in succession, like the feet of a caterpillar. This remark led me to examine the animal's motion with more accuracy, and on putting the hand under its belly, while the Snake was in the act of passing over the palm, the ends of the ribs were distinctly felt pressing upon the surface in regular succession, so as to leave no doubt of the ribs forming so many pairs of levers, by which the animal moves its body from place to place."

It is doubtless by the expansion of these ribfeet, and by the application of them alternately to the surface on which they move, that Serpents are able to glide with facility up the trunks, and along the branches of trees, a feat which we have seen the Colubride of America and the West Indies perform repeatedly, not (as absurdly represented in engravings) by encircling the tree in spiral coils, but gliding along with the body extended, exactly as a caterpillar crawls, but with far greater speed.

The earth is the sphere of activity of by far the greatest number of the Serpent races: they inhabit various situations, some frequenting woods, others heaths, and many preferring deserted buildings, old walls, and heaps of stones. A few species reside permanently among the foliage of trees; and others there are, which are truly aquatic, roving through the ocean even at considerable distance from the shores. These have the