76 
BULLETIN OF THE LABORATORIES 
rated laterad by the rhinalis fissure and mesad by the splenialis. The 
portion dorsad of these almost continuous fissures may be regarded as 
the dorsal lamina or mantle par excellence, while that part beneath 
contains the ventral lamina and alae. A large part of the ventral por- 
tion is devoid of cortex in the usual sense. The dorsal surface is 
divided into a small frontal lobe, which is circumscribed very deeply 
from the rest, and a large ovate parieto-occipital portion, which is not 
subdivided. 
The ventral portion is likewise divided into an anterior post-rhinal 
lobe occupying the region in front of the chiasm and fusing with the 
crus cephalad, and the large pyriform lobe with its modified cortex. 
The latter is expanded by the ventral part of the hippocampus into 
which it passes caudo-ventrad. 
The sylvian fissure is not pronounced and does not extend across 
the rhinalis fissure. A slight longitudinal depression extends longitu- 
dinally of the pyriform. This marks the course of the olfactory fibres 
and limits the non-cortical from the cortical portion. All of the region 
ventrad is devoid of a genuine cortex. Dorsad of it, the surface is 
occupied by olfactory fibres as far as to the rhinalis fissure. The 
mesad surface is separated by the splenialis or calloso-marginal fissure 
into a dorsal and ventral portion, but this fissure is relatively farther 
dorsad than the rhinalis by reason of the interpenetration of the thala- 
mus. Cephalad, the rhinalis and splenialis unite and cut off the pro- 
jecting frontal lobe from the crus beneath. 
There is a slight fissure where one might look for the callosal, but 
in the absence of that commissure it is but the union of the cortex of 
the gyrus fornicatus with the base. All beneath this fissure is devoid 
of true cortex and is continued caudad into the septum and corpus 
fornicis. (See Figs. 3 and 4, Plate A.) The splenialis grows deeper 
as it passes caudad, following the arch of the hemisphere until it lies 
in a dorso-ventral line. By comparing the longitudinal sections of 
Plate B with the transverse series of Plate A, the course of the fissure 
and the structure of the hippocampus will be perfectly obvious. The 
commissures are discussed beyond. 
The thalamus is about as in rodents. 
Minute Anatomy. 
Rhinenceplialon. The olfactory lobe, as a whole, is of relatively 
very large size, being expanded in all directions beyond the crus and 
especially produced cephalo-dorsad. No part of the dorsal part of the 
