The Nervous System. 



35 



vertebrates this portion of the brain is remarkable for the manner in 

 which its wall is differentiated. The ventral portion extends downward 

 as a slender funnel-like structure, the infundibulum, the tip of the latter 



h.c. 





'..v.m.b. 



b.o. 



'T- h. c.m.\ r v.(j,. 



b'.c r. 

 hyb 



Fifi. 23. Plan of the divisions of the vertebrate brain: A, embryonic; B, adult, 

 projection from dorsal surface ; C, adult, sagittal section. 



Primary divisions — PR, prosencephalon; T, telencephalon; DI, diencephalon ; 

 MS, mesencephalon; RH, rhombencephalon; MT, metencephalon ; MY, myelence- 

 phalon; S, spinal cord. 



a. a, cerebral aqueduct; b.o., olfactory bulb; cb., cerebellum; cm., nuimmillary 

 body; o.o., optic chiasma; c.p., pineal body; c.q., corpora quadrigemina; ep., epitha- 

 lamus; f.i., interventricular foramen ; h., hypophysis; h.c, cerebral hemisphere; 

 hyp., hypothalamus; inf., infundibulum; l.t., lamina terminalis; p., pons; p.c, 

 chorioid plexus of third ventricle: p.cr., cerebral peduncle; tv, thalamus, also in- 

 dicates position of massa intermedia; v.l., lateral ventricle; v.m.p., posterior 

 medullary velum; v.q., fourth ventricle. 



being in contact with the pituitary body or hypophysis and its base 

 connected with a small grey elevation, the tuber cinereum. Its cavity is 

 the recessus infundibuli. Immediately in front of the infundibulum the 



