NATURAL HISTORY OF SELBORNE. 



their articulations ; and thirdly, by the peculiar mobility and 

 connection of the ribs. 



" Numerous as are the vertebrae of the eel, the spine of which 

 consists of above a hundred, that of a serpent is in general formed 

 of a still greater number. In the rattle-snake (Crotalus Iwrridus}, 

 there are about two hundred ; and above three hundred have 

 been counted in the spine of the Coluber natrix. These vertebrae 

 are all united by ball-and-socket joints, as in the adult batracliia; 

 the posterior rounded eminence of each vertebra being received 

 into the anterior surface of the next. While provision has thus 

 been made for extent of motion, extraordinary care has at the 

 same time been bestowed upon the security of the joints. Thus 

 we find them effectually protected from dislocation by the 

 locking in above and below of the articular processes, and by 

 the close investment of the capsular ligaments. The direction 

 of the surfaces of these processes, and the shape and length 



VERTEUR.t: t)F SNAKK. 



of the spiuous processes, are such as to allow of free lateral 

 flexion, but to limit the vertical and longitudinal motions ; and 

 whatever degree of freedom of motion may exist between the 

 adjoining vertebra, that motion being multiplied along the 

 column, the flexibility of the whole becomes very great, and 

 admits of its assuming every degree and variety of curvature. 

 The presence of a sternum, restraining the motions of the ribs, 

 would have impeded all these movements, and would have also 

 been an insurmountable bar to the dilatation of the stomach, 

 which is rendered necessary by the habit of the serpent of 

 gorging its prey entire." 



In the Museum of the Eoyal College of Surgeons, Lincoln's 

 Inn Fields, is a very fine skeleton of the tiger boa, in which the 

 above ball-and-socket apparatus can be examined. It measures 

 eleven feet two inches, and has no less than two hundred and 



