2. The most eminent species of reptiles are Ser- 

 pests, which we may therefore particularly consider. 

 Their bodies are of a very peculiar make, having a 

 compages of bones articulated together. Here part 

 of the body is applied to the ground, and the other 

 part shot forward, which being applied to the ground 

 in its turn, brings the other after it. The spine of 

 their back variously writhed, helps their leaping, as 

 the joints of the feet in other animals.) They make 

 their leaps by means of the muscles that extend the 

 folds thereof. 



The number of joints in the back-bone are nu- 

 merous beyond what any one would imagine. la 

 the generality of quadrupeds they amount to not 

 above thirty or forty. In the serpent- kind, they 

 amount to a hundred and forty-five from the head 

 to the vent, and twenty-five more from that to the 

 tail. The number of these joints must give the back- 

 bone a surprising degree of pliancy ; but this is still 

 increased by the manner in which each of these 

 joints is locked into the other. In men and beasts 

 the flat surfaces of the bones are laid one upon the 

 other, and bound tight by sinews ; but in serpents 

 the bones play one within the other like ball and 

 socket, so that they have a full motion upon each 

 other in every direction. Thus if a man were to 

 form a machine composed of so many joints as are 

 in the back of a serpent, he would find it no easy 

 matter to give it such strength and pliancy at the 

 same time. The chain of a watch is but a bungling 

 piece of work in comparison. 



Though the number of joints in the back-bone, 

 is great, yet that of the ribs is still greater ; for, 

 from the head to the vent, there are two ribs to every 

 joint, which makes thei,r number two hundred anil 

 ninety in all. These ribs are furnished with muscles, 

 which being inserted into the head, run along to the 

 end of the tail, and give the animal great strength and 

 agility. 



The skin also contributes to its motions, being 



