522 THE MECHANICAL FUNCTIONS. 



aimed at in the construction of the pachydermata. 

 The hmbs have a great weight to sustain, in 

 consequence of the huge size of the body ; and 

 hence the several bones which compose the 

 pillars for its support are arranged nearly in 

 vertical lines. The joints of the elbow and knee 

 are placed low from the body ; the ulna in the 

 forelegs, and the fibula in the hinder, are fully 

 developed, and are distinct from the radius and 

 the tibia. The number of the toes, instead of 

 being reduced to one, as in the horse, or to two, 

 as in ruminants, is here increased to five : though, 

 in consequence of their being very short, and 

 of the skin which covers and surrounds them 

 being very thick, they hardly appear exter- 

 nally, and are distinctly recognised only in the 

 skeleton. 



It would carry me far beyond the limits of the 

 present work, were I to engage in a detailed 

 examination of all the varieties of forms and 

 structures that occur in the mechanism of the 

 different tribes of mammalia, in reference to the 

 purposes they are intended to serve, and to the 

 peculiar circumstances of the animal to which 

 they belong. I must necessarily pass over a 

 multitude of instances of express adaptation, 

 which are suited only to particular cases, and 

 are, consequently, of minor importance as regards 

 the general plans of organization. In the sort 

 of bird's-eye view which I am taking of the end- 



