ON THE BRAIN OF ATELES PANISCUS 503 
convex side receives that name, by its concave side bounds the sulcus 
in question: in other words, the eminentia collateralis stands in the 
same relation to 7 # as the hippocampus minor to //, or the hippo- 
campus major to # mm. From the region especially named by 
anatomists “eminentia collateralis,” the sulcus , x, which may be 
conveniently termed the ‘collateral’ sulcus, is continued forwards and 
backwards, and preserves, as might be expected, a similar relation to 
the parts which are the continuation of the eminentia collateralis, viz. 
the floors of the descending and posterior cornua respectively, as it 
had to that eminence. It is difficult to imagine a much more definite 
proof, if any were wanted, that the hippocampus minor is in no sense 
a continuation of the eminentia collateralis. 
In the brain whence the sections A to E were taken, the floors of 
both the descending and the posterior cornua were particularly broad 
(C, D); but even here the posterior cornu became a mere crescentic 
slit posteriorly (B). However, the continuation of the collateral’ 
sulcus was always directed upwards and outwards towards the bottom 
of the slit.t 
A comparison of the views here given, of the inner face and of 
sections, of Man’s brain, with, as nearly as possible, corresponding 
views of the brain of AZe/es (woodcuts, figs. I and 2) is exceedingly 
instructive. The principal sulci alone exist in <Ze/es; so that its 
brain furnishes a sort of sketch map of Man’s. The calloso-marginal 
sulcus, 7, 2, is ‘easily recognisable; so is the occipito-parietal sulcus, 
k, k; though the latter, instead of being straight and forming an 
obtuse angle with the plane of the corpus callosum, as in Man, is 
strongly convex forwards,” and, on the whole, makes an acute angle 
with the same plane. As a consequence, the occipital lobe (occ) is 
much larger, proportionally, than in Man, while the quadrate lobule 
is part passu smaller. The calcarine sulcus, /, 7, has the same general 
direction and the same bifurcated termination, as in Man. Anteriorly, 
it ends just in front of the level of the posterior edge of the corpus 
callosum (the prominent uncinate gyrus must be pushed aside to see 
1 T have recently had the opportunity of dissecting ten human brains, and, in all, I have 
found the calcarine and collateral sulci to present the relations described above, with perfect 
constancy. On the other hand, nothing could be more variable than the length and form of 
the posterior cornu of the lateral ventricle, and the relative and absolute size of the hippo- 
campus minor. In one of these brains—that of a negro—the posterior cornua were almost 
absent, not exceeding one-third of an inch in length on either side. In another the cornua 
were both 1} inch long and very wide, with a large hippocampus. Another had a posterior 
cornu 4 an inch long on the left side, 1 inch on the right. In yet another it was much 
longer on the right than on the left side, &c. 
2 T found this in both brains. M. Gratiolet represents the corresponding sulcus in 
A. belzebuth as nearly straight. 
