176 
no essential relation to the hippocampus, so that it would be wise 
to discard the use of the term hippocampal, as applied to the 
pyriform lobe, altogether. As examples of the confusion which 
such a nomenclature causes one might cite the examples of Her- 
rick and Bawden speaking of the hippocampus, when from the 
context they evidently mean the pyriform, and Beddard (1) call- 
ing the rhinal fissure hippocampal. 
On the lateral aspect of the hemisphere there will be noticed 
below the external olfactory radiation a large hemispherical mass 
(fig. 1, ¢.o.) of a pale-grey color and almost as large as the nati- 
form eminence. This is the twherculwm olfactorium. It will be 
more satisfactory if its description be deferred until the base of 
the brain is being described. The whole surface of the pyriform 
lobe and tuberculum olfactorium is pale, from the fact that they 
both receive a medullary coating in the form of arching white 
fibres from the external olfactory radiation. [The direction of 
these fibres is indicated in fig. 2 by a number of curved lines on 
the right side of the figure.] In all the brains which I have 
examined these fibres extend as high as the rhinal fissure, so that 
in a fresh brain of NVotoryctes almost the whole lateral aspect of 
the hemisphere would be white, as it is in Perameles. In all the 
Marsupial and Monotreme cerebra which I have examined histo- 
logically these radiating white fibres terminate both by means of 
naked end branchings and collaterals in relation to the pyramidal 
cells of the region. These cells, in addition to their large peri- 
pheral protoplasmic processes, are provided with large basal pro- 
cesses, and hence have been distinguished in the rabbit’s brain as 
“‘ Doppelpyramiden” by Koelliker (15). The fibres spreading out 
over the tuberculum olfactorium terminate in a similar manner in 
relation to the small multipolar cells of the region. 
THE BasaL SURFACE. 
The inferior aspect of the cerebrum is very irregular, and 
slopes downwards and backwards from the olfactory bulb to the 
natiform eminence. Immediately behind the olfactory bulb, 
there may be seen on either side of the middle line the huge 
protuberance forming the tuberculum olfactorium (fig. 2, ¢.0.). 
Bounding this laterally and posteriorly will be seen the crescentic 
external olfactory radiation (fig. 2, ¢.0.7.), which rapidly tapers 
as it is traced backwards and inwards to end in a little tubercle 
of grey matter (fig. 2, *), which is placed over the anterior ex- 
tremity of the nucleus amygdale. Behind the tuberculum 
olfactorium is the more laterally placed eminentia natiformis 
(fig. 2, pyr. 1.). As in Perameles and Erinaceus, all that can be 
seen of the base of the cerebrum belongs to the ‘“‘rhinencephalon’ 
of Turner (42). In animals a little higher in the scale of pallia 
