618 



THE HUMAN BODY. 



The Brain Regions in Front of the Midbrain. It would 

 be quite a hopeless task to attempt in a few pages any detailed 

 account of the topography of these, but in addition to the 

 facts already stated a few points of special physiological signifi- 

 cance may be indicated. These portions of the brain may 

 be in general described as consisting of three masses of gray 

 matter on each side ; optic thalamus, corpus striatum, cerebral 



Fl 



FIG. 177. Diagram to illustrate cerebral distribution of fibres proceeding from 

 the pes of the crus cerebri. For description see texr,. 



cortex. They are united in manifold ways by the transverse, 

 longitudinal, and oblique fibres of the white substance of the 

 cerebral hemisphere. Their more fundamental relations to 

 the midbrain and to one another are shown in a very sim- 

 plified and diagrammatic manner in Figs. 177 and 178. The 

 tier, or aqueduct of Sylvius, i, is seen passing into the pos- 

 terior end of the third ventricle, 3, which is separated by 

 only a very thin layer of white matter from the large ovoid 

 gray mass o, which is the optic thalamus. Connected by the 



