OF THE BONES OF THE TRUNK. 29 



this latter direction are modified by the formation of the 

 spinous processes. It is evident that this mobility must 

 diminish, as the latter have acquired a greater develop- 

 ment. In the Boa, the Tortrix, and in several of the genus 

 Coluber, Ophidians which possess the power of strongly 

 rolling up the body, the superior spinous processes are but 

 little developed, and the inferior are only found on the an- 

 terior part of the trunk. Other Ophidians, on the contrary, 

 and particularly the serpents properly called venomous, have 

 all the vertebrae bristling with spinous apophyses, both 

 above and below, extremely large, and of which the su- 

 perior are very broad and locked together. The develop- 

 ment of those parts varies even in species of the same 

 genus ; but we must defer the particulars to the de- 

 scriptive part of our book ; and I have here only to state 

 that, when the inferior spinous processes exist, generally 

 they are only found on the vertebrjie composing the 

 anterior parts of the trunk, reckoning from the heart. 



We have stated above that the vertebras of Ophidians, 

 with a few exceptions, are without transverse processes : 

 the analogous parts occur only in the Bungarus, where 

 they consist of two very slender lamellas on each side ; the 

 superior one little developed, and slightly oblique, the 

 anterior one rather considerable and wide at its extremity. 



A bony projection, placed on each side of the anterior 

 part of the body of the vertebrae, and directed a little 

 downwards, supports the articular facet of the ribs. These 

 bones, broad and compressed at their base, where they 

 present a small, blunt, apophysis, are almost cylindrical, 

 directed backwards, always arched, but in different degrees 

 in different species ; they vary in length according to the 

 circumference of the trunk which they are destined to em- 

 brace. The sternal extremity terminates in a cartilage, 

 which is continued on the edges of the abdominal plates. 



The external form of serpents indicates that the develop- 

 ment of the vertebrae, of their processes, and of the ribs, 

 should diminish tow^ards the two ends of the trunk ; 

 and hence the ribs of the first vertebra are very small, 

 or even entirely wanting. The Atlas, often unpro- 

 vided with a spinous process, has its body perforated by 



