52 AMERICAN FARMER'S HORSE BOOK. 



not have been of half the bulk of that of the horse. If the 

 dog had been the subject, it would have been very consider- 

 ably larger, comparing the general bulk of each animal. 

 This is singular. The human brain is largest in comparative 

 bulk; then the brain of the dog, the horse, the ox. Thus 

 would they be classed in the order of intelligence. 



" When the brain is cut, it is found to be composed of two 

 substances very unlike in appearance, (see m, in cut;) one, 

 principally on the outside, gray or ash-colored, and therefore 

 called the cortical (bark like), from its situation, and cineritious, 

 (ashen), from its color; and the other, lying deeper in the 

 brain, and from its pulpy nature, called the medullary sub- 

 stance. Although placed in opposition with each other, and 

 seemingly mingling, they never run into the same mass, or 

 change by degrees into one another, but are essentially dis- 

 tinct in construction as well as in function. 



" The medullary portion is connected with the nervous sys- 

 tem. The nerves are prolongations of it, and are concerned 

 in the discharge of all the offices of life. They give motion 

 and energy to the limbs, the heart, the lungs, the stomach, 

 and every part connected with life. They are the medium 

 through which sensation is conveyed ; and they supply the 

 mind with materials to think and work upon. 



" The cineritious part has a different appearance, and is dif- 

 ferently constituted. Some have supposed, and with much 

 appearance of truth, that it is the residence of the mind, 

 receiving tbe impressions that are conveyed to the brain by 

 the sensitive nerves, and directing the operation and action 

 of those which give motion to the limbs. In accordance with 

 this, it happens that, where superior intelligence is found, the 

 cineritious portion prevails, and where little beside brute 

 strength and animal appetite exist, the medullary portion is 

 enlarged. There is, comparing bulk with bulk, less of the 

 medullary substance in the horse than in the ox, and in the 

 dog than in the horse. The additional bulk of brain is com- 

 posed of cineritious matter. 



" From the medullary substance, as already stated, proceed 





