480 STRUCTURE OF THE HUMAN BRAIN. CHAP. xxiv. 



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 Gr. 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 Gr. St. Hilaire's work, that he 

 had been led by purely anatomical considerations to sepa 

 rate 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 Linnaeus. 



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 com 

 municated to the Linnasan 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 develope- 

 ment, 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 olfac 

 tory lobes and cerebellum, but they extend in advance of the 

 one and farther back than the other. Their posterior de- 

 velopement 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- 



