Neck, 2 Neck, 2 Neck, 2 Supporting ribs, 168 Supporting ribs, 252 With ribs, 249 Tail, 24 Tail, 50 Tail, 40 —— —— —— Total, 194 Total, 304 Total, 291 Though in form the ‘neck’ of a snake is often as undistinguishable as the tail—‘une tête sans col, et une queue, dont l’origine se confond avec le reste du corps,’ as Dumeril expresses it—there is the one invariable rule belonging to it, namely, that the first two joints of a snake’s spine are ribless, and that the ribs begin at the third. Physiologists tell us a snake has no neck, and for reasons which will be explained in the next chapter; yet, by way of distinction, all speak of ‘the neck’ as an accepted fact. No invariable rule as to tails can, however, be established, either as regards length, shape, or character. Firstly, the length of the tail varies from inches to feet in snakes of nearly the same size. Secondly, both venomous and harmless ones are occasionally furnished with horny tips, and both vibrate them with equal rapidity. Thirdly, snakes that have long _spineless_ tails also vibrate them rapidly; as do snakes with short spineless tails; so that one cannot say that spines are confined to one genus, any more than is their use or their action. The vibration of the tail is, in fact, only ‘an outlet for suppressed energy,’ as Professor Shaler of the United States has lucidly put it. Excitement displays itself in the tail of a snake as much as in the tail of a dog. This may be observed at the Ophidarium, or wherever an active snake can be watched. In the rattlesnake it is, of course, more conspicuous, and always audible when agitated; but many others similarly display their feelings in their eloquent caudal terminations. A handsome young python, of about eight feet long, at the Zoological Gardens, has a tail of which the last few inches taper so suddenly that the extreme end of this reptile appears almost ludicrously trivial for so fine a possessor. One inch of this—hardly thicker than a rat’s tail—you may see wriggling so rapidly that you can scarcely follow its movements, or believe that it is a part of the large quiescent body to which it is attached. In pursuit of its prey the python itself glides with slow dignity, while the trifling little terminal inch or so of tail is in a perpetual but most _un_dignified wriggle. In the ‘Racer,’ already familiar to the reader, the tail is one-fourth the length of the body; in the ‘milk snake’ (_Coluber eximius_), introduced in chapter iv., it is one-fifth. The extensive variation in tails may be comprehended by their number of vertebræ, which in some snakes amount to 200, and in others are reduced to 5.