1883.] NATURAL SCIENCES OF PHILADELPHIA. 183 



The sections are imperfect in the forward portion of the root 

 of the Diencephalon (diatela); they do not show the j^ostcommis- 

 sura, described b}' Stieda and Wilder. The prsecommissxira^ h.as 

 its usual shape and position. 



The relations of the Diencephalon to the Prosencephalon are 

 shown in figs. 7, 8 and 9. The procoelife extend back into the 

 posterior sections of the hemispheres. Anterior to this the hemi- 

 spheres fuse with the thalami below, receiving from the upper 

 portion of the Diencephalon a conspicuous band of fibres (fig. 8, a). 

 The relations of the dia- to the procoeliae are best obtained by 

 means of horizontal longitudinal sections ; these have not been 

 made as yet, so that the nature of these cavities is somewhat 

 doubtful. It appears that the procoeliaj communicate with each 

 other some distance anterior to the lamina terminalis. 



The hemispheres have a great lateral extent, containing exten- 

 sive cavities. Their posterior halves are partly fused together ; 

 anteriorly, however, they are quite separate and distinct, becoming 

 more c^'lindrical in section in the region of the Rhinencephalon. 

 A peculiar feature of each proccelia is the formation of a short 

 superior median cornu (fig. 11, a); corresponding to this is an 

 extension of the gray matter lining the cffilia to the cortex of the 

 hemisphere. Forwards the coelise have a vertical and more in- 

 ternal position. The Rhinencephala arise in masses of gra}' cells 

 in the anterior third of the lateral portions of the hemispheres ; 

 they do not contain anj- cavit^-jbut are continued forward into the 

 solid olfactory nerve. 



The structure and distribution of the nerve-fibres and cells 

 have not been closely studied ; the following are some preliminary 

 notes : 



The cavities of the brain are throughout lined with masses of 

 nerve-cells of varying thickness. Nerve-cells are also found 

 scattered among the fibres, but these are somewhat rare. The 

 gra}' substance lining the hemispheres corresponds to the central 

 gra>y^ the Hohlengrau of Meynert. At a few points it is found 

 upon the brain cortex; these are : (1) the lateral bodies of the 

 infundibulum (fig. 3) ; (2) the upper surface of the central portion 

 of the hemispheres (fig. 11) ; (3) and the inner sides and front of 

 the foremost portion of the same (fig. 12) ; (4) the cerebellum. 



' Anterior and posterior commissures. 



