144 ANATOMY OF VERTEBRATES. 



Miclas Marmoset is to the body as 1 to 20 ; in the Gorilla it is as 

 1 to 200. 



But such ratios do not show the grade of cerebral organisation 

 in the Mammalian class: that in the Kangaroo is higher than 

 that in the Bird, though the brain of a Sparrow be much larger in 

 proportional size to the body : and the Kangaroo's brain is superior 

 in superficial folding and extent of grey cerebral surface to that of 

 the Petaurist. The brain of the Elephant bears a less proportion 

 to the body than that of Opossums, Mice, and proboscidian Shrews, 

 but it is more complex in structure, more convolute in surface, and 

 with proportions of pros- to mes-encephalon much more nearly 

 those in the human brain. The like remark applies to all the 

 other instances above cited. 



The weight of the brain, without its membranes, in a full- 

 grown male Gorilla is 15 oz. avoird. I estimate that of the entire 

 body as being nearly 200 lbs. : in the relatively larger brains of 

 the small species of Quadrumana the convolutions are fewer, or 

 may be absent, as in Midas. 



In Man alone is a bulk of body, greater than in any Quadru- 

 mana save Gorilla, associated with a large size as well as with the 

 highest stage of complexity of the cerebral organ. This is, 

 perhaps, the most notable and significant fact in Comparative 

 Anatomy. 



The weight of the brain in the adult male averages about 

 49 oz. avoird., and ranges from about 35 oz. to 65 oz. In the 

 adult female the weight of the brain averages about 43 oz. 

 and a half, and ranges from 32 to 54 oz. The mean difference 

 is thus about five ounces and a quarter. The brain has advanced 

 to near its term of size at about ten years, but it does not usu- 

 ally obtain its full development till between twenty and thirty 

 years of age, and undergoes a slight decline in weight in advanced 

 life. 1 



The brain, without dura mater, of an Australian female, of 

 5 feet 3 inches high, weighed 32 oz. ; that of a Bushwoman, 

 5 feet high, is estimated, in Lin", 2 at 30*75 oz. In European 

 females the brain has been found as low in size ; but the requisite 

 observations to determine the range and the average of cerebral 

 development have hitherto been made only on Europeans. 3 The 

 weight of the brain of the male Hottentot, 3 lbs. 2 oz. avoird., 

 dissected by Wyman, 4 encourages the expectation of analogous 



1 If the capacity of a cranium in cubic inches be ascertained, a fair and instructive 

 notion of the weight of the brain may be obtained by estimating that of a cubic inch 

 of it at 25957 grains. 2 lviii '. 3 xlix", l", lxi". * l\ui". 



