107 



tliese parts represent each tlie consolidation of two 

 digits, i. e., the second and third in one, the fourth 

 and fifth in the other, the fact of there being but 

 ,one bone in the cannon of these animals may show 

 that all the bones having, in this case, digits to 

 -carry are consolidated into one for action upon 

 them, and corroborate the supposition that the 

 splent bones in the horse remain separate as the 

 unemployed connections of two discarded digits in 

 its foot. 



§ 105. It will be well, perhaps, before giving a 

 description of the diaphi'agm to make some allu- 

 sion to the lungs, although a more detailed exami- 

 nation of their functions will be made further on. 



It has been remarked (§ 76) that when the 

 snake's ribs are fuUy under the influence of the 

 double turns given them in the " superimposition 

 of twists," then the chest has its greatest possible 

 capacity, and that as a consequence of this the 

 lungs, which fill the chest, are then expanded to 

 their greatest limit. 



If this air be forcibly detained within them 

 dming action, the lungs will form an elastic cushion, 

 w^hich expands after every compression. They 

 thus, Hke the fly-wheel in machinery, make good 

 £Lny deficiency in force from other sources at every 



