458 THE MECHANICAL FUNCTIONS. 



seps, animals frequently met with in the South 

 of France, and which have four minute feet, 

 totally inefficient for the support of the body, 

 and only remotely useful in contributing to its 

 progressive undulations. 



Ascending from these, we may form a series of 

 reptiles, in which the developement of the limbs 

 becomes more and more extended, till we arrive 

 at Crocodiles, in which they attain a consider- 

 able degree of perfection. As a consequence of 

 this greater developement of the skeleton, we 

 find the trunk divisible into separate regions. 

 We now, for the first time, meet with a distinct 

 neck, separating the head from the thorax, 

 which is itself distinguishable from the abdomen ; 

 and a distinct sacrum is interposed between the 

 lumbar and the caudal vertebrae. 



A further approach to the higher classes, is 

 observable in the number of cervical vertebrae, 

 which is almost constantly seven ; as we shall 

 find it to be in the mammalia. The articula- 

 tions of the vertebrse are similar to those of 

 serpents, inasmuch as they consist of ball and 

 socket joints. In that of the occipital bone with 

 the first vertebra of the neck, we find that 

 nature again reverts to the simpler form of a 

 single condyle projecting from the body of the 

 occipital bone, instead of lateral condyles pro- 

 ceeding from its leaves, as we noticed was the 



