NERVOUS CENTRES. (HUMAN ANATOMY. THE ENCEPHALON.) 



665 



2 Ibs. 9 oz. 1 dr. I have generally found the 

 cavity of the skull smaller in old men than in 

 middle-aged persons. It appears to me, there- 

 fore, probable that the brain really decreases in 

 old age, only more remarkably in some persons 

 than in others. 



" 5. There is undoubtedly a very close con- 

 nection between the absolute size of the brain 

 and the intellectual powers and functions of the 

 mind. This is evident from the remarkable 

 smallness of the brain in cases of congenital 

 idiotismus, few much exceeding in weight the 

 brain of a new-born child. Gall, Spurzheim, 

 Haslam, Esquirol, and others have already ob- 

 served this, which is also confirmed by my own 

 researches. The brain of very talented men, 

 on the other hand, is remarkable for its size. 



" Anatomists differ very much as to the weight 

 of the brain compared with the bulk and weight 

 of the body; for the weight of the body varies 

 so much, that it is impossible to determine 

 accurately the proportion between it and the 

 brain. The weight of an adult varies from 100 

 to 800 Ibs., and changes both in health and 

 when under the influence of disease, depending 

 in great measure on nutrition. The weight of 

 the brain, although different in adults, remains 

 generally the same, unaltered by the increase 

 or diminution of the body. Thin persons 

 have, therefore, relative to the size of the 

 body, a larger brain than stout people. 



" From my researches I have drawn the fol- 

 lowing conclusions. 



" 1 . The brain of a new-born child is, rela- 

 tively to the size of the body, the largest ; the 

 proportion is 1 : 6. 



" 2. The human brain is smaller, in compa- 

 rison to the body, the nearer man approaches to 

 his full growth. In the second year the pro- 

 portion of the brain to the body is as 1 : 14; in 

 the third, 1:18; in the fifteenth, 1 : 24. In 

 a full-grown man, between the age of twenty 

 and seventy years, as 1 : 35 to 45. In lean 

 persons the proportion is often as 1 : 22 to 27; 

 in stout persons, as 1 : 50 to 100 and more." 



(This estimate, as far as regards the early 

 ages, differs from that of Dr. John Reid, pro- 

 bably owing to the difference in the number 

 weighed.) 



" 3. Although Aristotle hasremarked that the 

 female brain is absolutely smaller than the male, 

 it is nevertheless not relatively smaller com- 

 pared with the body; for the female body is, 

 in general, lighter than that of the male. 

 The female brain is for the most part even 

 larger than the male, compared with the size 

 of the body. 



" The different degree of susceptibility and 

 sensibility of the nervous system seems to de- 

 pend on the relative size of the brain as com- 

 pared with the body. (qu. ?) Children and 

 young people are more susceptible, irritable, 

 and sensitive than adults, and have a relatively 

 larger brain. Thin persons are more suscep- 

 tible than stouh In diseases which affect the 

 nourishment of the body, the susceptibility 

 increases as the patients grow thinner. The 

 susceptibility and sensibility decreases, on the 

 other hand, with persons recovering from a 



long illness, gradually as they regain their 

 strength. The degree of sensibility in animals 

 is also in proportion to the size of the brain. 

 Mammalia and birds have a larger brain and 

 are more susceptible than amphibious animals 

 and fishes."* 



Enough has been said to show, that in con- 

 trasting the brain of man and that of the lower 

 animals, with reference to the much agitated 

 question of the connexion of mental faculties 

 and intellectual endowments with that organ, 

 no one standard of comparison must be se- 

 lected. We must look to absolute and relative 

 size we must compare the bulk of the several 

 portions of the encephalon with each other 

 we must notice the size of the encephalic 

 nerves in relation to the whole organ and, 

 above all, we must compare the intimate or- 

 ganization of brain one with the other. Unless 

 all the features of the brains that are subjected 

 to comparison be carefully taken into the ac- 

 count, erroneous conclusions will be obtained. 

 For instance, the brain of the elephant is ab- 

 solutely larger than that of man : the convo- 

 lutions of the hemispheres are very highly de- 

 veloped, and exhibit a degree of complexity 

 almost equal to that of the human brain. At 

 first sight we might be led to infer a very close 

 approximation to the human, and place the 

 elephant very high up in the scale of cerebral 

 developement. In comparing, however, the 

 brain of this animal with that of the monkey, 

 the following result is obtained. The encepha- 

 lon of the elephant is above that of the monkey 

 by the superior developement of the cerebral 

 convolutions ; it is equal to it, as regards the 

 quadrageminal bodies, but from the general 

 form of the brain, the length of its transverse 

 diameter, the presence of olfactory eminences, 

 the position of the cerebellum (uncovered by 

 the posterior lobes), it must be placed on a level 

 with that of the inferior Mammalia.f 



Of the brain in different races of mankind. 

 When so much diversity is observable in the 

 form of the cranium in different races of man- 

 kind, it seems reasonable to expect a corres- 

 ponding variety in the shape and other charac- 

 ters of the encephalon. The external form of 

 this latter organ will correspond with that of the 

 cranium, and its size with the capacity of that 

 cavity. But it is plain that as the capacity of 

 the skull is no wise necessarily affected by its 

 shape, so the absolute bulk of the brain need 

 not vary, although its containing case may ex- 

 hibit much variety of form. The great ques- 

 tion for the physiologist to determine is, whe- 

 ther, in the various races of mankind, the brain 

 exhibits any striking peculiarities, characteristic 

 of one or more of them, or whether it presents 

 no more variety of shape, size, weight, and 

 structure than may be observed in different in- 

 dividuals of any one of those races. 



It should be premised that actual observa- 

 tions of the brain of different races are few. 

 In Europe, where hitherto anatomy has chiefly 



* Tiedemann on the Brain of the Negro com- 

 pared with that of the European and the Chang 

 Otang. Phil. Trans. 1836. 



t Leuret, op. cit. p. 448. 



