102 



lated to tlie actions of the liead condyles (§ 92) and 

 to those of the lower jaw, which latter will be more 

 fully considered hereafter. 



§ 102. It will be observed that, regarding the 

 fore and hind limbs as ribs, the counter torsions in 

 their length can no longer, as in the real ribs, be 

 received by the elasticity of their substance ; ac- 

 cordingly, separate joints are substituted for elas- 

 ticity. Again, were the bearings mere bevels 

 (§ 51), the passage from one to the other would be 

 very rough ; and, unless the bevels were very 

 broad, quite insufficient for the extent of motion. 

 This is remedied by the formation of the foot of 

 tlie higher animals. In these, however, it is un- 

 necessary that the first digit appear as an actual 

 appui, if they rest on four feet ; it is only in man, 

 and, to some extent in a few other animals, that 

 the development and spreading inward of the great 

 toe renders possible the steady change in the S S, 

 as their forces cross the median* line without any 

 support from anterior appuis. 



To still further assimilate the perfection of sup- 

 port to that which the snake gains from a completely 

 underlying set of appuis, it is necessary that the 



* Any shoe which inteiferes with this inward spread of the great toe 

 is a hindrance to marching. 



