BEFORE discussing the most remarkable of all ophidian caudal appendages, the _Crotalus_ rattle, and the many speculations regarding it, we will enumerate some other acrobatic achievements of which snakes are capable; as, in accounting for these, some interesting facts appertaining to their anatomical structure can be described. A humorous journalist has said, ‘There is apparently nothing that a snake can _not_ do, except swallow a porcupine.’[63] Presuming that he alludes to physical feats, he is not far from wrong. For all that, the Western pioneers of America tell us of yet one more thing that these reptiles cannot accomplish, and that is, cross over a rope of horse-hair. Having by accident discovered that they turn aside from this, some Western settlers, when camping out, have effectually entrenched themselves within a circle of horse-hair rope as a barrier to rattlesnakes while sleeping. Let us try to account for this. Many of my readers have seen the cast-off coat of a snake. Those who have not can have the pleasure of examining one or several the next time they go to the Zoological Gardens, where the obliging keeper will cheerfully exhibit them. Others at a distance may not enjoy this facility, and for these the accompanying diagrams may be a slight compensation. [Illustration: Portion of slough of a rattlesnake (exact size). Ventral scales of the same, and a section.] The whole cuticle or epidermis of a serpent is composed of these overlapping scales, of which the above illustrations are only fragments. Thus when we speak of their _scales_, we do not mean distinct and separable laminæ, like the scales of some fishes, each of which may be scraped or plucked off, and which overlie each other like the feathers of birds. The covering of a snake is one entire piece, loose-fitting, and so arranged as to lie in those scale-like folds which accommodate themselves to every movement of the body. The ventral or under scales are, in fact, a regular kilting, as may be seen by the section; and the upper ones correspond somewhat with what our lady friends call the shell or the leaf pattern in knitting work. The outer or exposed folds are stronger, thicker, and more hardened than the inner parts, just as the knitter ‘throws up’ her pattern with a coarser wool or larger needles, and knits the less conspicuous parts in a softer material. The naked space of thinner skin between these scales being very considerable, one can therefore easily understand how, when a snake would attempt to pass over a horse-hair rope, the sharp, prickly hairs, standing out _chevaux-de-frise_ fashion, would insinuate themselves unpleasantly in those softer and more vulnerable interstices which become exposed by the sinuations of the body. Probably, if we knew it, or had an opportunity of observing, we should ascertain that snakes do not crawl over furze bushes, or thistles, or the prickly pear (_opuntia_), or any similar vegetation of tropical climates, and for