MAMMALIA. 165 



exist more for conferring muscular power than sensation, and the portions reaching 

 the broad flat surface on the extremity are very diminutive ; it therefore appears that 

 the tail is not only a powerful instrument for motion, but for defence, and that it is 

 capable of giving hard blows without feeling much pain ; it is on this account furnished 

 with just as much nerve as will produce a moderate perceptiveness, something between 

 that of skin and horn. 



The number of cervical vertebrae being always the same in mammalia, when the 

 neck is long the nerves are placed at a proportionately greater distance from each 

 other ; if therefore the four inferior had always entered the axillary plexus, as in man, 

 some of them must have been conducted to it in a manner quite incompatible with the 

 free motion of the spine and the upper extremity ; so that it is generally composed 

 of fewer and larger nerves, and so long as there is the same regularity in the origin 

 of the fibrils from the spinal cord, their collection into few or many nerves, or into 

 larger or smaller, is of no importance, for in the hedgehog the whole body receives its 

 nerves from a spinal cord, occupying only a small part of the spinal canal. In the 

 fox, the two cords forming the median nerve do not unite at the upper part of the 

 humerus, as in man, but at the lower, at a very acute angle ; there is, however, some 

 variation in different subjects, and even the two limbs of the same. 



In simiae, the nerves of the palm of the hand are small in proportion to those 

 in man, and do not terminate in such thick brushes of filaments at the tips of the 

 fingers, and therefore are not near so well calculated for perfecting the sense of touch. 

 They are, however, a little larger than those of the foot. The nerves derived from 

 the radial branch of the spiral, and the dorsal of the ulnar, supplying the back of the 

 hand and fingers, are much larger in proportion to the same in man. The sense of 

 touch in different animals is variously modified by the shape of the foot, as well as by 

 the structure of the skin, and is frequently so much altered as to possess merely 

 common feeling. In many animals, as the anterior extremities exist principally for 

 supporting the body, the large branches of the fifth spread on the snout answer the 

 purpose of the sense of touch, but are smaller when the nerves of the fingers approach 

 the proportion of those in man. 





