1910.] On a Mesoccelic Recess in the Human Brain, etc. 



517 



wall of the supra-pineal recess is greatly folded to form a choroid plexus {c.p.), 

 and above and below it lie large veins {v). The lower surface of the posterior 

 commissure is covered, in the middle line, by the peculiar high columnar 



Fig. 1. — Mouse. Saofittal Section through the Region of the Posterior Commissure, &c. 

 X 60. (The lines ah, cd, indicate approximately the planes of the transverse sections 

 represented in figs. 2 and 3.) 



c. c, corpus callosum ; c. p., choroid plexus ; i.p. r., infra-pineal recess ; o. I., optic 

 lobe ; p. c, posterior commissure ; p. g., pineal gland ; pit, isolated invaginated 

 patches of the epithelium of the sub-commissural organ ; r.f., Reissner's fibre ; 

 3. c, superior commissure ; s.c. o., sub-commissural organ ; s.p. r., supra-pineal recess ; 

 v., veins. 



2 R 2 



