842 PROFESSOR DAVID HEPBURN ON 
higher levels presented the ridges and depressions which are the characteristic of the 
claustrum, and it was only after the sections had passed below the level of the general 
mass of the lenticular nucleus that the claustrum was seen as a separate structure, with 
a definite external capsule between it and the more deeply placed grey mass. Indeed, 
the appearance of striation, which was directed forwards and outwards, was more 
definite below the level at which the lenticular nucleus still retained its biconvex 
outline and while the striated substance intervened between the claustrum and the 
head of the caudate nucleus. The effect of this disposition of the grey and white 
masses of the corpus striatum was to suggest that the differentiation of the external 
capsule was incomplete and had not advanced to the stage of separating the claustrum 
from the lenticular nucleus. 
A band of white substance intervened between the cortical grey matter and wavy 
margin of the claustrum, and, since the claustrum is usually regarded as a detached and 
submerged portion of the grey cortex of the insula, it would appear the white fibres 
which separate the grey cortex from the claustrum are developed earlier than those 
which, in the higher brains, separate the claustrum from the caudate nucleus and are 
known as the external capsule. In TURNER’s account of the elephant seal, it does not 
appear that he submitted his specimen to this dissection. The grey nature of the tail 
of the caudate nucleus was always distinct, and an extension of the sections through the 
optic thalamus revealed quite plainly its grey substance, bounded laterally by the 
posterior limb of the internal capsule. The grey matter, however, did not resolve itself 
into the subordinate nuclei (anterior, mesial, and lateral) which characterises the 
human brain. 
The Pineal Body.—I was able to examine three specimens of this interesting object, 
and in each case it presented widely different characters. Indeed, the differences were 
so pronounced that they were not easy to reconcile and certainly not easy to explain. 
In the brain which I removed from the skull of the seal which was two days old 
at the time of its death, the pineal body was a large prismatic object resting upon the 
vermis of the cerebellum and wedged into the interval between the occipital ends of 
the cerebral hemispheres. It projected about 27 mm. behind the splenium of the 
corpus callosum. The peduncle broke in the process of removal, but it was very short 
and apparently just sufficiently long to permit the expanded part to clear the splenium. 
The dimensions of the expanded, prismatic part were as follows:—greatest length, 
27 mm.; width, 18 mm. ; vertical depth, 12 mm. 
In a second specimen, belonging to one of the adult brains, the peduncle was again 
broken, but the expanded part still occupied its natural position. In this case the 
peduncle was cylindrical and the expanded end was pyriform in shape, its measurements 
being :—length, 20 mm.; width, 15 mm. ; vertical depth, 9 mm. It showed no signs of 
faceting by pressure from surrounding structures, as might have been expected, 
supposing the reduction in its size as compared with the young specimen to have 
resulted from the effects of preservative solutions. In the third specimen, also that 
