Page:The Zoologist, 4th series, vol 5 (1901).djvu/330

302 The first is an active physiological process on the part of the serpent, as the result of which the external covering is separated from the true skin. Prof. Packard describes this separation as being due to the growth of fine temporary cuticular hairs. Thus loosened, the slough rapidly becomes dry, and is ready to be cast off. The second stage, or the casting off, is a mechanical process, by which the serpent endeavours to rid itself of what is now no longer a part of its anatomy. This is effected by continuous rubbing against any convenient surface, the side of the cage in the case of captive snakes. The result of this rubbing, as far as the slough is concerned, depends, in my opinion, on the simple factor of whether the serpent is in a position to rub off both sides of the slough evenly—that is to say, if the reptile can get pressure evenly exerted on both sides of the body—by creeping through grass, or in some other way—the slough will peel off whole, being turned inside out in the process; but if, on the other hand, any projecting point should come in contact with one side of the slough, the latter, being very delicate, will be torn, and the slough cast in pieces. In very young, and therefore small snakes, the slough comes off very readily, and generally entire; but in older and larger specimens I have found it the exception rather than the rule for this to occur, and the slough is usually in pieces. This is quite independent of the state of health of the snake, a matter which is, moreover, somewhat difficult of diagnosis, unless the reptile is suffering from canker. I have made a point of observing this sloughing in reptiles in various zoological collections, and invariably have seen the sloughs of the larger serpents in pieces in the cages. Anyone can observe it at the Zoo. It is particularly noticeable in the Pythons; and I now append a series of notes made by Mr. W.J. Clarke, of Scarborough, on the frequency and character of the sloughings of one of his Pythons:—

Python molurus.—Sloughing in confinement (W.J. Clarke, Scarborough).

"I received the Python on Sept. 7th, 1897. Three weeks later I found one morning that it had shed its slough, but, not expecting this, made no notes. Python now measured 6½ ft.

"1. On Nov. 20th, 1897, at 7 p.m., Python entered the water in its zinc bath. Remained there continuously till 11 p.m. on