io6 



BRAINS OF RATS AND MEN 



intimate with the overlying pallial field than with the underlying 

 striatum. 



Johnston (1923) has pointed out that this dorsal ventricular 

 ridge consists of two parts which are dissimilar in origin, in func- 

 tion, and in their definitive arrangement in the mammahan brain. 

 (i) The anterior part (hypopallium of Figs. 21, 22, 23) is ana- 



neral cortex 



S^^hijpopollium 

 ig^\g|^\ bippocQnnpQi cortex 

 l^i^i^^-j-pLjriform cortex 



^^^^^2-4-9 'obus' pallidas 

 >?/;-.-:"':' / oi-focto-striotum 



lateral forebrain bundle 

 optic tract 



Fig. 23. — Cross-section through the middle of the cerebral hemi- 

 sphere of the box-tortoise. 



tomically and physiologically closely related with the overlying 

 general cortex above the rhinal fissure. The "pallial thickening" 

 of Figures 22 and 23 is a transitional sheet of cells interposed 

 between the general cortex and the hypopallium. (2) The pos- 

 terior part (amygdaloid ridge of Figs. 21 and 24) is similarly re- 

 lated with the pyriform cortex along the line of the amygdaloid 

 fissure which is a backward extension of the endorhinal fissure. 

 It is added to the older primitive amygdala which lies ventrally of 

 it. Johnston calls the anterior part of the dorsal ventricular ridge 

 "caudate nucleus"; but this is confusing because the definitive 



