96 VERTEBRA AND JAWS OF SNAKES. 



and is furnished at one end with a ball and at the other with a corresponding socket, 

 into which the ball of the succeeding vertebra exactly .fits, thus enabling the creature 

 to writhe and twine in all directions without danger of dislocating its spine. This ball- 

 and-socket principle extends even to-. -the ribs, which are jointed to certain rounded 

 projections of the vertebrae in a manner almost identical with the articulation of the 

 vertebrae upon each other, and as they are moved by very powerful muscles, perform 

 most important functions in the economy of the creature to which they belong. 



Sometimes the Snakes advance by a series of undulations, either vertical or hori- 

 zontal, according to the species, and when they proceed through water, where the 

 scales of the abdomen would have no hold of the yielding element, their movements 

 are always of this undulatory description. The number of vertebrae, and con- 

 sequently of ribs, varies much in different species, in some Snakes being about three 

 hundred. 



The jaws of the serpents are very wonderful examples of animal mechanics, and may 

 be cited among the innumerable instances where the existing construction of living 

 beings has long preceded the inventions of man. We have already seen the invaluable 

 mechanic invention of the ball-and-socket joint exhibited in the vertebrae of the Snakes, 

 and it may be mentioned that in the spot where the limbs of almost all animals, man 

 included, are joined to the trunk, the ball-and-socket principle is employed, though in 

 a less perfect manner than in the Snakes. It is by means of this beautiful form of 

 joint that posture-masters and mountebanks are able to contort their bodies and limbs 

 into so many wonderful shapes, the muscles and tendons yielding by constant use and 

 enabling the bones to work in their sockets without hindrance. Indeed, a master of 

 the art of posturing is really a useful member of society, at all events to the eye of the 

 physiologist, as showing the perfection of the human form, and the wonderful capabil- 

 ities of man, even when considered from the mere animal point of view. 



In the jaw of the serpents, we shall find more than one curious example of the man- 

 ner in which human inventions have succeeded, if, indeed, they have not been borrowed 

 from some animal structure. 



All the Snakes are well supplied with teeth ; but their number, form, and structure 

 differ considerably in the various species. Those Snakes that are not possessed of 

 venomous fangs have the bones of the palate as well as the jaws furnished with teeth, 

 which are of moderate size, simple in form, and all point backward, so as to prevent 

 any animal from escaping which has ever been grasped, and acting as valves which 

 permit of motion in one direction only. 



The bones of the jaws are, as has already been mentioned, very loosely constructed, 

 their different portions being separable, and giving way when the creature exerts its 

 wonderful powers of swallowing. The great python Snakes are well known to swallow 

 animals of great proportionate size, and any one may witness the singular process by 

 taking a common field Snake, keeping it without food for a month or so, and then giv- 

 ing it a large frog. As it seizes its prey, the idea of getting so stout an animal down 

 that slender neck and through those little jaws appears too absurd to be entertained for 

 a moment, and even the leg which it has grasped appears to be several times too large 

 to be passed through the throat. But by slow degrees the frog disappears, the mouth 

 of the Snake gradually widening, until the bones separate from each other to some dis- 

 tance, and are only held by the ligaments, and the whole jaw becoming dislocated, 

 until the head and neck of the Snake look as if the skin had been, stripped from the 

 reptile, spread thin and flat, and drawn like a glove over the frog. 



No sooner, however, has the frog fairly descended into the stomach, than the head 

 begins to assume its former appearance ; the elastic ligaments contract and draw the 

 bones into their places, the scales, which had been far separated from each other, re- 

 sume their ordinary position, and no one would imagine, from looking-.at the reptile, to 

 what extent the jaws and neck have recently been distended. As many of the Snakes 

 swallow their prey alive the frog for example, having been heard to squeak while in 

 the stomach of its destroyer the struggles of the internal victim would often cause its 

 escape, were it not for the array of recurved teeth, which act so effectually, that even if 

 the Snake wished to disgorge its prey it could not do so. Mr. Bell had in his collection a 



