BRAIN OF MAMMALIA. 17 



and the smallest adult human brain he ever met with exceeded this 

 weight by fourteen ounces and a quarter ; yet the nerves on the base of 

 the former were of ten times greater magnitude than were those on the 

 base of the latter. " It must not, however, be concluded," he ob- 

 serves, " that Man has smaller nerves than any other animal. In order 

 that my ideas may be better understood, I shall state the following 

 hypothetical case : Suppose the ball of the eye to require six hundred 

 nervous fibrils in one instance, and three hundred in another, though 

 only half the size of the former ; and farther, that the eye with six hun- 

 dred fibrils possesses a brain of seven, and that with three hundred of only 

 five, drachms ; to the latter we ought to ascribe the largest brain, and a 

 more ample capacity of registering the impressions made on the organs 

 of vision ; for, allowing one drachm of brain to each hundred fibrils, 

 the brain which is absolutely the least will have a superfluous quantity 

 of two drachms, while the larger has only one. That the eye, which is 

 supplied with a double quantity of fibrils may be a more complete organ 

 of sense, may be readily admitted, but the remark is inapplicable to the 

 point in question." 



The statement of Soemmerring, that Man possesses a larger brain than 

 any other animal, compared with its nerves, is probably correct. It is, 

 however, by no means an established fact, that nerves of the same mag- 

 nitude do require the same proportion of brain for the exercise of their 

 respective functions ; or that the same nerve in different animals demands 

 an equal quantity ; or, farther, that the proportion of brain required by a 

 large nerve, is greater than that required by one of inferior size. More- 

 over, to say that the size of the brain, compared with its nerves, affords 

 an index of the differences existing between Man and the lower animals, 

 or between different animals, with regard to intellectuality, is an assump- 

 tion unsupported by solid proof. 



After all, the most striking characteristic of the human brain consists in 

 the prodigious development of the cerebral hemispheres no animal, what- 

 ever may be the proportion which the brain bears to the body, affording a 

 parallel. Not any quadruped approaches Man in the magnitude of the he- 

 misphere of the brain ; namely, that part of the organ, which serves as the 

 principal instrument of the intellectual operations. Hence arises the cor- 

 responding development of the anterior portion of the cranium ; the index, 

 at the same time, of the development of the cerebral hemispheres, and of 

 their predominance over the portion of the cerebral mass devoted to the 

 external senses ; and hence, also, is the volume of the cranium in Man 

 greater, compared to that of the face, than in any other mammal. 



Allusion has already been made to the low condition of the brain of 

 the Marsupialia : with this condition is associated a parallel inferiority of 

 intellect. The low grade of development of the brain in these animals is 



