284 ON THE RELATIONS OF MAN 



than these do even from the Monkeys, and that the differ- 

 ence between the brains of the Chimpanzee and of Man is 

 almost insignificant, when compared with that between 

 the Chimpanzee brain and that of a Lemur. 



It must not be overlooked, however, that there is a 

 very striking difference in the absolute mass and weight 

 between the lowest human brain and that of the highest 

 ape a difference which is all the more remarkable when 

 we recollect that a full grown Gorilla is probably pretty 

 nearly twice as heavy as a Bosjes man, or as many an 

 European woman. It may be doubted whether a healthy 

 human adult brain ever weighed less than thirty-one or 

 two ounces, or that the heaviest Gorilla brain has exceeded 

 twenty ounces. 



This is a very noteworthy circumstance, and doubtless 

 will one day help to furnish an explanation of the great 

 gulf which intervenes between the lowest man and the 

 highest ape in intellectual power ; * but it has little 



* I say help to furnish : for I by no means believe that it was any 

 original difference of cerebral quality, or quantity, which caused that 

 divergence between the human and the pithecoid stirpes, which has 

 ended in the present enormous gulf between them. It is no doubt 

 perfectly true, in a certain sense, that all difference of function is a 

 result of difference of structure ; or, in other words, of difference in 

 the combination of the primary molecular forces of living substance ; 

 and, starting from this undeniable axiom, objectors occasionally, 

 and with much seeming plausibility, argue that the vast intellectual 

 chasm between the Ape and Man implies a corresponding structural 

 chasm in the organs of the intellectual functions ; so that, it is said, 

 the non-discovery of such Vast differences proves, not that they are 

 absent, but that Science is incompetent to detect them. A very 

 little consideration, however, will, I think, show the fallacy of this 

 reasoning. Its validity hangs upon the assumption, that intellectual 

 power depends altogether on the brain whereas the brain is only 

 one condition out of many on which intellectual manifestations 

 depend ; the others being, chiefly, the organs of the senses and the 

 motor apparatuses, especially those which are concerned in pre- 

 hension and in the production of articulate speech. 



A man born dumb, notwithstanding his great cerebral mass and 

 his inheritance of strong intellectual instincts, would be capable of 

 few higher intellectual manifestations than an Orang or a Chim- 

 panzee, if he were confined to the society of dumb associates. And 

 yet there might not be the slightest discernible difference between his 

 brain and that of a highly intelligent and cultivated person. The 

 dumbness might be the result of a defective structure of the mouth, 

 or of the tongue, or a mere defective innervation of these parts ; 

 or it might result from congenital deafness, caused by some minute 

 defect of the internal ear, which only a careful anatomist could 

 discover. 



