502 Dr. F. W. Mott and Miss A. M. Kelley. [ Mar. 6, 
and posteriorly by the hippocampal fissure, and anteriorly by that portion of 
the Sylvian fissure which lies below the rhinal fissure. 
Characteristics (fig. 12)—The depth of the cortex is about 13 mm. It is 
thus considerably more shallow than the cortex of the neopallium, which 
measures, over most of its extent, about 2 mm. in depth. The molecular 
layer is comparatively deep, measuring about 0°3 mm. The pyramidal layer, 
which is about 0°6 mm. deep, is rather scantily filled with large angular 
cells, which stain well, and have long branching processes. The cells of the 
superficial layer are particularly noticeable. They are of characteristic 
irregular triangular or quadrate shapes, and often lie with the base towards 
the surface, with two, or even more, long branching processes passing 
upwards. Staining well, and lying closely crowded together, they form a 
conspicuous line at the top of the pyramidal layer. Below the pyramids a 
pallid zone can be seen measuring about 0°2 mm. There are a few granules 
scattered here and amongst the pyramids, but there is no definite granule 
layer. The polymorph layer is about 0-4 mm. deep. 
The Hippocampal Fissure—Several distinct types of cell arrangement can 
be observed within the hippocampal fissure. Their position will be best 
explained by referring to the diagrams. Fig. 4 is a section of the temporal 
lobe of a right hemisphere. On it will be seen the olfactory type of cortex 
between the hippocampal fissure and the rhinal fissure, and, externally, type 
“R” lying between the olfactory and the temporal types. Within the 
hippocampal fissure, and hidden from view on the surface by the basal 
ganglia, a narrow gyrus is shown, in section. The cortex on this gyrus was 
found to be of the same type as the limbic (wide fig. 13), though somewhat 
mcre shallow (perhaps owing to pressure within the fissure). The types 
a, b, ¢, d, figured in No. 14, are found in the positions marked a . . . a: 
6b... b, etc., respectively on fig. 4, the last evidently corresponding to the 
stratum granulosum of the human brain. 
The Olfactory Tract.*—The molecular layer is deep and contains islets 
of small angular cells. The cells of the next layer are larger and are still 
very angular in shape; they have fine processes, stain well, and are rather 
closely crowded together. Under a low power it can be seen that this layer 
is arranged in a zigzag fashion. There are a number of irregularly scattered 
large angular cells below this layer. This structure seems to correspond 
to the tuberculum olfactorium described by Ramon y Cajal and Campbell. 
* See footnote * on p. 495. 
