92 AYES. 



the ox and sheep. The striated septum, from its structure, has some commissural 

 peculiarities in consonance with a differently-formed brain, but may only combine the 

 visual powers with those of the other senses, like the anterior crus of the fornix in 

 mammalia. It is the only general combining medium in the place of the great com- 

 missure and fornix. It associates the parts of its corresponding hemisphere concerned 

 in sensitive functions, but the two hemispheres communicate so slightly through it as 

 to be in a great degree independent of each other, like the exterior or motive regions 

 in mammalia. 



In birds the brain and cerebellum are larger than in amphibia, but the intellect is 

 not much higher. The brain has fewer and less extensive parts for ministering to 

 sensation and ther intellect than in mammalia generally. By far the largest portion of 

 the brain belongs to the external or motive region, and corresponds with the greater 

 required variety of motion. Some muscular force is necessary for respiration, but 

 large flexors and extensors must be provided for the motions of the wings and legs. 

 As the dorsal portion of the spine is so fixed, there is a great saving of voluntary 

 muscular power, which would otherwise have been necessary for keeping it sufficiently 

 firm in accordance with the vigorous motions of the limbs. Therefore, although the 

 motive region is in a great degree the largest, the entire dimensions of the brain must 

 have been further increased, as in mammalia, if the spine had throughout permitted 

 corresponding motions, and the actions of the limbs had depended on its assistance 

 through muscular power for their support in the several modes of progression. 



