CEREBRAL COMMISSURES 



123 



two^is at the posterior end of the corpus callosum, the hippocampal commissure 

 (or, in other words, the upper part of the lamina terminalis) is stretched and 



FIG. 166. GBAPHIC RECONSTRUCTION OF THE MESIAL, HEMISPHERE -WALL 



OF A FOETUS 5'6 MM. LONG. (After His.) 



P, stalk of hemisphere ; c. v, anterior and posterior parts of trapezoid area (area paraterminalis) ; 

 Li., lamina infrachoroidea of mesial hemisphere-wall below, c.f., choroidal fissure; Icm, limbus of 

 mesial hemisphere-wall below, h.f., hippocampal fissure ; c.c, corpus callosum ; l.t., lamina terminalis ; 

 ., anterior commissure ; f, commencing column (anterior pillar; of fornix ; rh, olfc 



rt.r. 



olfactory stalk. 



c/. 



rh 



l.t. a.c. un 



FIG. 167. GRAPHIC RECONSTRUCTION OF THE MESIAL HEMISPHERE-WALL OF A FOETUS 



OF 8-3 CM. LONG. (After His.) 



P, stalk of hemisphere; c.s., cavum septi; b, fimbria, continuous with /, fornix; Icm, limbus; 

 <'.c., corpus callosum ; h.f. 1 , callosal fissure ; h.f.' 2 , hippocampal fissure ; c.f., calcarine fissure ; un, uncus ; 

 (i.e., anterior commissure ; l.t., lamina terminalis ; o.c., optic commissure ; rh, olfactory stalk ; ves, oiiuline 

 of cavity of hemisphere. 



drawn into a horizontal position forming the psalterium or lyra, while the area 

 paraterminalis is also drawn out to form the apical portion of the septum pellucidum 

 (Elliot-Smith and others). According to the other view, the increase in length is 



