96 VEKTEBllyE 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 horizontal, 

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

 abdomen woiild have no hold of the yielding element, their movements are always of 

 this undulatory description. The number of vertebrae, and consequently 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 an useful member of society, at all events to the eye of the physio- 

 logist, as showing the perfection of the human form, and the wonderful capabilities 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 

 manner 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 giving 

 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 distance, 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, resume 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 small Snake which 



