126 



THE HUMAN BODY. 



the median line and behind the posterior commissure of the 

 middle ventricle is a little body nearly conical, which anato- 

 mists have named the pineal gland or conarium, from its re- 

 semblance to a pine-cone. 



A mass of white substance forms the central portion of 



Fig- 33. Section of the cncephalon in the median line. 



A. Plane of the great fissure. 



B. Corpus callosum. 



C. Optic bed. 



D. Pans Varolii, wider which is seen 



the medulla oblongata. 



E. Spinal cord continued, from the me- 



dulla oblongata. 



F. Section of cerebellum, showing tJie 



"tree of life" 



G. Left hemisphere of the cerebellum. 



both hemispheres, and this is covered over in every part by 

 the gray or cortical substance. 



The brain is composed then, essentially, of a central 

 nucleus, and two great lobes or hemispheres. The several 

 parts of this nucleus differ in their texture, in the proportion 

 of the gray and white substances, and in the disposition of 

 these two substances in their tissues; but they all present 

 fibres which are common to all, which penetrate and unite 

 them before extending to the two hemispheres. 



The mass of the entire encephalon is proportionally greater 



