OF THE CEEEBEUM OF THE QUADEUMANA. 
191 
taken the most prominent part of the convex border of the hippocampus major as the 
limit between the antero-median and the posterior portions of the cerebrum. The 
former includes the anterior and middle cornua of the ventricle, the corpus striatum, 
thalamus opticus, and the hippocampus major ; the latter, the posterior cornu and hippo- 
campus minor, where these exist. In Man and the Quadrumana, the angle formed at the 
junction of the hippocampus major and minor readily indicates the exact spot on which 
to place the compasses (see Plate III. fig. 7). Such measurements should, if possible, 
he taken before the brain is removed from the cranial cavity. Let the length of the first 
part be called A, and that of the second B. In Man the average proportion in several 
examples of A to B is as 100 to 53. In this Orang’s brain A measures exactly 2 inches, 
and B 1 inch, or as 100 to 50 ; so that the posterior lobe, as defined by internal structure, 
exhibits the same slight diminution upon that of the human brain, as was already esti- 
mated by the amount of covering of the cerebellum. It must be remembered, however, 
that this observation is taken from a spirit preparation. 
Preshytes Imcojprymnus {Ot^o ). — An adult female died in the Zoological Society’s Gar- 
dens, August 20, 1861, and the brain was examined while in a perfectly fresh condition. 
The posterior lobes completely covered, and projected beyond, the cerebellum. The 
sulci on the internal face of the cerebral hemisphere (Plate II. fig. 2) bear a very close 
resemblance in general aii’angement (though of course far less complex) to those of the 
human brain. The occipito-parietal {Jc, Ji) runs downwards and forwards, and almost 
meets the calcarine (/, 1), the second internal annectent gyrus scarcely appearing on the 
surface. The calcarine sulcus differs from that, not only of Man, but of nearly all 
Apes, in extending to the extremity of the lobe, and even turning round to the outer 
surface, without dividing into branches. The three sections show that this sulcus 
penetrates more deeply into the substance of the hemisphere than in Man, but it is 
tolerably simple in its course, passing nearly directly inwards. The posterior cornu of 
the ventricle is distinctly open to vrithin a very short distance of the hinder extremity 
of the lobe, and is of considerable vertical depth, being curled round the very promi- 
nent calcarine involution, or hippocampus minor. 
In the left hemisphere a horizontal section was made, so as to expose the lateral 
ventricle (Plate III. fig. 5, a). The posterior cornu was seen, when opened from above, 
to take the same general course as in the brain of Man, viz. outwards, backwards, and 
finally somewhat inwards, but, owing to the depth of the calcarine fissure, and conse- 
quent great projection of the hippocampus minor, it is placed nearer to the external 
wall of the hemisphere than it is in Man. The measurements of the antero-median (A) 
and posterior (B) portions of the hemisphere are 1‘5 inch and *7 inch — A to B as 100 
to 47. The latter is therefore proportionally less than in the human brain. 
Cercopithecus. — Several examples of this genus have come under examination, in- 
cluding C. sabcBus, C. ruber ^ and C. mona, but a description of C. pygerythrus (F. Cuv.), 
the common Vervet Monkey, will suffice. In order to obtain a side view of the brain 
in situ, the right half of the cranium of an adult animal of this species was carefully 
