838 PROFESSOR DAVID HEPBURN ON 
Another ‘unexpected result was, that at the level mentioned, viz. about 4 mm. 
above the corpus callosum, the section opened into the cavity of the lateral ventricle, 
which therefore rose to a higher level than the mesial surface of the corpus callosum, 
and consequently there must be a corresponding deviation from the horizontal direction 
of those fibres of the corpus callosum which form the roof structures in relation to the 
body of the cavity of the lateral ventricle. This upward extension of the ventricle, 
taken in conjunction with the large size of the convolutions as indicated by the depth of 
the fissures, shows that notwithstanding its superficial dimensions the brain of the seal 
falls considerably short of a human brain of similar size as regards the amount of grey 
and white matter. 
In addition to what has already been stated with regard to the corpus callosum, the 
following additional facts may be noted. The mesial faces of the two hemispheres were 
so closely in apposition that opposing gyri practically interlocked with each other, and 
therefore the dorsal surface of corpus callosum was entirely concealed. When this 
surface was exposed it showed feeble stax longitudinales mediales and still feebler 
laterales. The cingulum was present, but much smaller than the size of the surrounding 
gyri led me to anticipate. The forceps major and forceps minor were easily dissected 
and were of characteristic appearance. 
On removing the roof of the lateral ventricle and of its cornua I was impressed by 
the apparent simplicity of the basal ganglia, which were large, and at the first glance 
suggested strongly such appearances as one is familiar with in the human brain. Taking 
into consideration the somewhat elaborate and intricate condition of the convolutions 
of the pallium, the simple nature of basal objects was remarkable. The anterior or 
frontal cornu of the lateral ventricle was very shallow. Its course was outwards and 
forwards into the substance of the frontal lobe, where it terminated in a blind recess. 
Its relations to the septwm lucidum and to the caput of the nucleus caudatus were 
similar to the arrangements seen in the human brain. 
The middle or descending cornu likewise followed the human plan in its chief 
features and direction. On its floor there were the choroid plexus, the fimbria hippo- 
campt, and the hippocampus major terminating in the pes hippocampi. The choroid 
plexus was continuous with the pia mater of the dentate sulcus, and thus, as in man, the 
termination of this cornu was situated on the lateral aspect of the crus cerebri and closed 
by the ependyma ventriculorum. The choroid plexus, however, was wider than in man, 
and spread itself out so as to form a vascular sheet which separated the objects in the 
roof of this cornu from the other structures on its floor. Further, the hippocampus 
major and the fimbria, ‘with the overlying choroid plexus, were pressed upwards against 
the roof of the cornu, where they adapted themselves to a deep furrow which was 
bounded mesially by the optic tract and laterally by the tail of the caudate nucleus. 
Again, on its convex margin the hippocampus major was separated from the floor of 
the cornu by a deep fissure which almost completely detached this object from the floor 
of the cornu. Indeed, the connection between the hippocampus major and the floor of 
