98 ON CLASSIFICATION. 



" In man the brain presents an ascensive step in develop- 

 ment, higher and more strongly marked than that by which the 

 preceding snb-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 fur- 

 ther back than the other. Their posterior development 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." — L. c, pp. 19, 20. 



These are the assertions which have been repeated over and 

 over again during the last few years ; but, thanks to the exer- 

 tions of the able Conservator of your Museum, it is in my 

 power to lay before you visible and tangible facts, which prove 

 these assertions to be wholly devoid of foundation. 



The third lobe, characterised bv extending further back 

 than the cerebellum, is said to be "peculiar to the genus 

 Homo." 



I place before yon casts of the cranial cavity, accurately re- 

 presenting the relative positions of the parts of the brain of a 

 Gorilla, of a Chimpanzee, of an Orang, of a Cynocephalus ; and 

 you observe that the posterior, or third lobe, of each projects 

 further back than the cerebellum, in just the same sense as a 

 man's can be said to do so ; and in some cases, as in the baboon, 

 to a much greater extent. 



The assertion that the third lobe, as defined by Professor 

 Owen, is " peculiar to man," is therefore demonstrably contrary 

 to fact. 



" Equally peculiar is the posterior horn of the lateral ventricle." 



Side by side upon the table are two dissections, made in the 

 same way, the one of the brain of an Orang-utan, the other that 

 of a man, taken at hazard by Mr. Flower, who has been good 

 enough to dissect both (Fig. 40). 



Every one in this theatre, I imagine, can see perfectly well 

 that the Orang has a posterior cornu, which, in proportion to the 

 size of its brain, is just as long and nearly as much incurved 



