NOTE-BOOK OF A NATURALIST. 355 



In the skeleton of the largest python in the museum 

 of the Royal College of Surgeons of England, which 

 measures sixteen feet six inches in length, there are 

 three hundred and forty-eight vertebrae. Of these, two 

 hundred and seventy-nine support free or moveable ribs, 

 the rest are caudal vertebrae. When the serpent begins 

 to advance, the ribs of the opposite sides are drawn apart 

 from each other, and the small cartilages at the end of 

 them are bent upon the upper surfaces of the abdominal 

 scuta, on which the ends of the ribs rest. The ribs move 

 in pairs, and the scute under each pair is necessarily 

 carried along with it. The scute lays hold of the ground 

 by its posterior edge, and becomes a fixed point for 

 renewed progression. Sir Everard Home, who gives this 

 description of the serpent's motion, remarks that it is 

 beautifully seen in climbing over an angle to get upon 

 a flat surface ; and so it is. Nor will the observer find 

 many species, not even excepting the pythons and boas, 

 in which it is very well seen, where this subcuticular 

 multipedous mode of going through the world is more 

 visibly manifested than in the puff adders.* But Sir 

 Everard justly says, that the large abdommal scuta of the 

 boa may be considered as hoofs or shoes, best fitted for 

 this kind of progressive motion. 



Sir Everard further shows, that there are five sets of 

 muscles which bring the ribs forward. One set goes 

 from the transverse process of each vertebra to the rib 

 immediately behind it, which rib is attached to the next 

 vertebra. The next set starts from the rib a little way 

 from the spine, just where the former terminates, passes 

 over two ribs, sending a slip to each, and is inserted into 

 the third : a slip also connects it with the next succeed- 

 ing muscle. Under this comes the third set, arising from 

 the posterior side of each rib, and passes over two ribs, 



Clotlio arietans. 



