494 ON THE BRAIN OF ATELES PANISCUS 
have proved the existence of the three structures referred to in the 
Chimpanzee and the Orang, by investigations upon the brains of 
these animals, undertaken with especial reference to the questions 
under discussion ; and I propose to continue the process of rectifica- 
tion thus commenced, by inquiring into another special case—that of 
Ateles paniscus—and proving, by direct demonstration of the facts, 
that the three structures, said to be absent even in the highest Apes, 
are, on the contrary, largely developed! in this comparatively low 
American monkey, possessed of but a rudimental thumb upon its 
hand, and provided with four more teeth than the Old World Apes 
and Man. 
In fact, so far from its being true that the differences between 
Man and the Apes lie mainly in the cerebral characters, so often 
referred to, all the evidence now accumulated tends towards the 
belief that the only three, very striking, cerebral characters, absent in 
other Mammalia, which can be truly affirmed to be common to Man 
and the Old and New World Szmze, are exactly these three,—the 
whole of the true Apes, so far as our present knowledge goes, 
possessing a posterior lobe, a posterior cornu to the lateral ventricle, 
and a hippocampus minor in that posterior cornu; while these 
structures, so far from being in a rudimentary condition, are often 
more largely developed, in proportion to other parts of the brain, in 
the Apes than in Man. 
The figures 1 and 2 of Plate XXIX. [Plate 36] represent the 
brains of a male and of a female AZe/es of about the same size, as 
seen from above: both figures were drawn under my own eye by a 
very competent artist, and are in all essential respects perfectly 
faithful. It is nevertheless obvious that they differ greatly—so much, 
in fact, that they might readily be supposed to have belonged to 
different species. The whole difference, however, is due to the 
circumstance that, while fig. I was drawn from an almost fresh brain, 
fig. 2 represents a brain which has been for several months in spirit. * 
The roundness of outline of the latter as compared with the former, 
1 Since this paper was read, Mr. Marshall, F.R.S., has published, in the third number of 
the ‘ Natural History Review’ (July 1861) a valuable essay on the Chimpanzee’s brain, illus- 
trated by photographs of the parts said to be absent ; and Mr. Flower, in a paper read before 
the Royal Society (June 20th, 1861), has demonstrated over again the presence of the same 
parts in the Orang’s brain, has shown their large development in Cedws, and has even proved 
the presence of a large posterior cornu and of a hippocampus minor in the Lemurine 
Otolicnus | 
2 The brain of Ateles belzebuth, figured by M. Gratiolet, pl. 10, figs. 1, 2, 3, 4, has under- 
gone the same alteration as that represented in my fig. 2, as might be expected from the fact 
of its having been long preserved in spirit. 
