Whether the Structure of the Human Brain entitles Man to Form a distinct Sub-class of the Mammalia.
When, in consequence of these and many other zoological considerations, the order Bimana had already been declared in 1856, by Isidore G. St. Hilaire, in his history of the science above quoted (p. 473), 'to have become obsolete,' even though sanctioned by the great names of Blumenbach and Cuvier, the reader may imagine the surprise excited in the scientific world when Professor Owen announced, in the year following the publication of G. St. Hilaire's work, that he had been led by purely anatomical considerations to separate Man from the other Primates and from the mammalia generally as a distinct sub-class, thus departing farther from the classification of Blumenbach and Cuvier than they had ventured to do from that of Linnæus.
The proposed innovation was based chiefly on three cerebral characters belonging, it was alleged, exclusively to Man, and thus described in the following passages of a memoir communicated to the Linnæan Society in 1857, in which all the mammalia were divided, according to the structure of the brain, into four sub-classes, represented by the kangaroo, the beaver, the ape, and Man, respectively:—
'In Man, the brain presents an ascensive step in developement, 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 overlap the olfactory lobes and cerebellum, but they extend in advance of the one and farther back than the other. Their posterior developement is so marked, that anatomists have assigned to that part the character of a third lobe; it is peculiar to the genus Homo, and equally peculiar is the "posterior horn of the lateral ventricle" and the "hippocampus minor" which characterises the hind-lobe of each hemisphere. The super-
