476 ON THE RELATIONS OF MAN WITH THE LOWER ANIMALS 
of experts, and hence, in all probability, to be regarded as more 
strictly scientific :— 
“In man, the brain presents an ascensive step in development, 
higher and more strongly marked than that by which the preceding 
sub-class was distinguished from the one below it. Not only do the 
cerebral hemispheres (figs. § and 6 A) overlap the olfactory lobes and 
cerebellum, but they extend in advance of the one, and further back 
than the other (fig. 6, C). Their posterior development is so marked, 
that anatomists have assigned to that part the character of a third 
lobe; 7 zs peculiar to the genus Homo, and equally peculiar ts the 
postertor horn of the lateral ventricle, and the ‘hippocampus minor, 
which charactertse the hind lobe of each hemisphere. Peculiar mental 
powers are associated with this highest form of brain, and their con- 
sequences wonderfully illustrate the value of the cerebral character ; 
according to my estimate of which I am led to regard the genus 
Homo as not merely a representative of a distinct order, but of a 
distinct sub-class of the Mammalia,! for which I propose the name of 
‘ Archencephala’ (fig. 6).” 
It might be a grave question whether, granting the existence of the 
differences assumed to distinguish the human brain, they would justify 
the establishment of a sub-class for the genus Homo , but that difficulty 
is not worth discussing, inasmuch as I shall endeavour to demonstrate, 
in the course of the following pages, the accuracy of the three counter 
statements which I made to the audience assembled in Section D, 
viz. :— 
1. That the third lobe is neither peculiar to, nor characteristic of 
man, seeing that it exists in all the higher Quadrumana. 
2. That the posterior cornu of the lateral ventricle is neither pecu- 
liar to, nor characteristic of man, inasmuch as it also exists in the higher 
Quadrumana. 
3. That the Hippocampus mrnor is neither peculiar to, nor charac- 
teristic of man, as it is found in certain of the higher Quadrumana. 
I support the first two propositions by the evidence of every original 
observer who has written upon the subject, including Professor Owen 
himself, and by my own personal observations. The third rests upon 
the evidence of Messrs. Schroeder van de Kolk and Vrolik, and of an 
eminent countryman of our own, Dr. Allen Thomson, to whom I am 
indebted for unpublished observations made with express reference to 
these very points. 
1. The third lobe or posterior lobe of the cerebrum.—Many anato- 
1 Tere occurs the note which I have already quoted at p. 464. The italics in the above 
extract are my own. 
. 
