PART I.-PHYSIOLOGY. 



CHAPTER I— The Skeleton. 



The bony parts of the snake consist of a skull, a loiig 

 vertebral column and ribs. The vertebrae are very numerous, 

 varying from about 120 to upwards of 400 in the body ; 

 those of the tail number from 4 or 5 in some burrowing 

 snakes to as many as 200 in certain tree snakes, in no case 

 exceeding the dorsal vertebrae in number.* The vertebrse, 

 Plate I, figs. 2 aqd 3, are proocelous, i. e., the bodies are articu- 

 lated by ball and socket joints, the socket being in front 

 of the body; the movement of each joint is limited by 

 other minor joints between the adjacent 'apophyses' (or 

 protuberances) of each pair of vertebrae ; but, as a whole, the 

 vertebral column is capable of extensive motion in every 

 direction. Of the numerous apophyses the most obvious 

 are the posterior or ' neural' spine and the anterior spine or 

 ' hypapophysis.' The neural spines are most prominent in 

 some venomous snakes ; in Bunga7'us fasciatus they are 

 unusually large and are firmly connected with the skin. 

 The anterior spines are susceptible of a peculiar modifica- 

 tion ; in the genera Elachistodon (India) and Dasypeltis 

 (Africa) those of the cervical vertebrae penetrate the gullet 

 and act as pharyngeal teeth ; several of them are tipped 

 with dental crust. 



* There may possibly be exceptions. I have found a specimen of 

 the common green tree-snake to have 172 dorsal and 169 caudal 

 vertebrae, the tail being four-tenths of the entire length, 



