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 Maynmalia. 



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 Avorld 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 gene- 

 rally as a distinct sub-class, thus departing farther from the 

 classification of Blumenbach and Cuvier than they had ven- 

 tured to do from that of Linnaeus. 



The proposed innovation was based chiefly on three cere- 

 bral characters belonging, it was alleged, exclusively to Man, 

 and thus described in the following passages of a memoir 

 communicated to the Linnsean Society in 1857, in which all 

 the mammalia wei^e 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 develop- 

 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- 

 velopment 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 jieculiar is the ' posterior horn of 

 the lateral ventricle' and the ' hippocampus minor' which 

 characterizes tlie hind-lobe of each hemisphere. The super- 



