OF THE BONES OF THE TEUNK. 
20 ' 
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 vertebrse 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 vertebrae composing the 
anterior parts of the trunk, reckoning from the heart. 
We have stated above that the vertebrae 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 lamellae 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 towards 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 
