458 



J. B. JOHNSTON 



^ .Vjv.-::>;VtV'i:.-:\.v-V*i 



n.o.a':- 



Figs. 56 to 62 Rat, seven transverse sections of the hippocampal region ros- 

 tral to the interventricular foramen. Magn. 40 diam. 



Fig. 56 Section through the rostral end of the hippocampus in the olfactory- 

 peduncle. 



Fig. 57 Section through the rostral part of the olfactory tubercle showing 

 the special medial hypertrophy of the deep cells of the tubercle. Between it and 

 the hippocampal cortex the deep cells come out to the surface as the primordium 

 hippocampi. In all the sections of the rat it is particularly noticeable how the 

 primordium appears as a continuation of the deep or polymorphic layer of the 

 hippocampus. 



Fig. 58 Section showing the indusium bending around the genu. Note the 

 large cells of the polymorphic layer. Below the genu nearly all the cells, deep 

 as well as superficial, are pyramidal in form and there is a distinct hippocampal 

 fissure and in-curving of the cortex. 



Fig 59 Section caudal to genu. Note the extent of the hippocampal cortex 

 and that its deep or polymorphic layer is now part of the primordium and will 

 continue back over the foramen as the bed of the hippocampal commissure. 



