ON THE RELATIONS OF MAN WITH THE LOWER ANIMALS 431 
his yet appeared upon the conformation of the brain in the higher 
Mammalia—the “ Mémoire sur les plis Cérébraux de l’Homme et des 
Primates,” by M. P. Gratiolet,—I find the following passage (p. 2) :-— 
“The convoluted brain of man and the smooth brain of the mar- 
moset resemble one another in the fourfold character of a rudimentary 
olfactory lobe, a posterior lobe, which completely covers the cerebellum, 
a well-marked fissure of Sylvius, and lastly, @ posterior cornu to the 
lateral ventricle. These characters are met with in combination only 
in man and in the apes.” 
M. Gratiolet’s beautiful original figures of the brain of the chimpan- 
zee (Pl. vi), and of the orang (PI. vii), show quite clearly that the 
hinder margin of the cerebral lobes in these animals, when the brain 
is in its natural condition, overlaps the hinder margin of the cere- 
bellum. 
Many months ago, having learned that my friend Dr. Allen Thomson 
had at one time occupied himself with the dissection of the brain of the 
chimpanzee, I applied to him for information, and he has very kindly 
allowed me to print the following extracts from his letters. Of the first 
brain he examined—that of a young female chimpanzee, seven or eight 
months old,—this eminently careful anatomist and physiologist says 
(under date of May 24, 1860) :— 
“There is, very clearly, a posterior lobe, separated from the middle 
oné by as deep a groove between the convolutions on the inner side of 
the hemispheres, as in man, and equally well marked off on the other 
side. I should be inclined to say, that the posterior lobe is little 
inferior to that of man, excepting, perhaps, in vertical depth. The 
cerebral hemispheres completely covered the cerebellum, as seen from 
above. I took pains to observe this while the brain was still within 
the cranium, looking down upon it at right angles to the longitudinal 
axis of the cranial cavity, and I found the posterior extremity of the 
cerebral hemispheres projected a little beyond the vertical line, passing 
the back of the cerebellum.” 
Thus, every original authority testifies that the presence of a third 
lobe in the cerebral hemisphere is not “ peculiar to the genus Homo,” 
but that the same structure is discoverable in all the true Simiz among 
the Quadrumana, and is even observable in some lower Mammalia; and 
any one who chooses to take the trouble to dissect a monkey’s brain, or 
even to examine a vertically bisected skull of any of the true Simiz, 
may convince himself, on the still better authority of nature, not only 
that the third lobe exists, but that it extends to the posterior edge of, 
if not behind the cerebellum. 
2. The postertor cornu.—in the “ Icones,” already referred to, Tiede- 
VOL, II Il 
