NERVOUS SYSTEM. (NERVOUS CENTRES. THE ENCEPHALON.) 



664 



The general conclusions deducible from the 

 preceding statements are, that the human brain 

 readies and maintains its highest degree of de- 

 velopement between the ages of 20 and 60 ; 

 that the female brain is materially smaller than 

 that of the male ; that the proportion of the 

 weight of the brain to that of the body de- 

 creases with age, and the most marked 

 diminution in tins respect takes place between 

 the ages of 20 and 30 years, although it has 

 already begun at 5 years, and occurs very de- 

 cidedly at from 13 to 15 years; and lastly, that 

 the great preponderance of the human brain 

 over that of most of the lower animals depends 

 upon the great developement of the cerebrum 

 and cerebellum. 



It was formerly admitted, pretty generally, 

 that the human brain was larger, both abso- 

 lutely and relatively to the size of the body, 

 than that of any other animal. This assertion, 

 however, must now be received with some mo- 

 dification. Exceptions to its superiority in ab- 

 solute weight are found in the elephant and 

 the whale. The brain of an African elephant, 

 seventeen years old, which was dissected by 

 Perrault, weighed 9 Ibs.* The brain of an 

 Asiatic elephant weighed, according to Allen 

 JVloulins, lOlbs.f Sir Astley Cooper dissected 

 an elephant's brain, which weighed 8 Ibs. 1 oz. 

 2 grs. (avoirdupois.)J Rudolphi found that 

 the brain of a whale, 75 feet long, ( Balana 

 mysticetus,) weighed 5 Ibs. 10 oz., and that 

 that of a narwhal ( Monodon monoceros,) 17 to 

 18 feet long, had a weight of 2 Ibs. 3 oz. And 

 there are likewise exceptions to the statement 

 that the human brain is larger than that of other 

 animals, relatively to the size of his body. 

 Pozzi has shewn (as quoted by Tiedemann) 

 that many small birds (for instance, the spar- 

 row) have, in comparison to the size of their 

 body, a larger brain than man ; and Dauben- 

 ton, Haller, Blumenbach, and Cuvier, found 

 the brain of some of the smaller apes of the 

 Hodentia, and singing birds, relatively to the 

 size of the body, larger than in man.|| 



" We must seek for the cause of man's su- 

 periority," says Tiedemann, " not merely in the 

 greater bulk of his brain in comparison to that 

 of his body, but regard must also be had to the 

 size of his brain with respect to the bulk and 

 thickness of his cerebral nerves, and likewise 

 to the degree of perfection in its structure. 

 Soemmehng was the first to show that the 

 human brain, in comparison to the size and 

 thickness of the nerves, is larger than that of 

 any other animal, even the elephant and whale, 

 both of which have an absolutely larger brain 

 than man. Blumenbach's, Obels', Cuvier's, 

 Treviranus', and my own researches have suffi- 



* Descr. Anatom. d'un Elephant, Mem. de 

 l'Ac;ul. des Sciences He Paris, t. iii. 



t An anatomical account of an Klephant. Lend. 

 1682. 



} Quoted in Tiedemann's paper on the Brain of 

 the Megro. Phil. Trans. 1836. 



$ Obscrvat. Anatom. de Cerebro, an sit inhomine 

 proportione m;ijus, quam in aliis animalibus ? 



|| Tiedemann's paper on the Frain of the Negro, 

 before quoted. See also Leuret'sTal>!6, Anat. Comp. 

 du Sysjtcme Nerveux, t. i. p. 4*20. 



ciently corroborated this. It is also satisfac- 

 torily shewn that the organization of the human 

 brain is far superior to that of any other animal, 

 not even excepting those apes which bear the 

 closest resemblance to man." 



The following conclusions, which Tiedemann 

 deduces from his observations, are so impor- 

 tant that I cannot refrain from inserting them 

 here.* 



" l.The weight of the brain of an adult male 

 European varies between 3 Ibs. 2 oz. and 4 Ibs. 

 6 oz The brain of men who have distinguished 

 themselves by their great talents is often very 

 large. The brain of the celebrated Cuvier 

 weighed 3 Ibs. 11 oz. 4 dr. 40 grs. avoirdupois, 

 or 4 Ibs. 11 oz. 4 dr. 30 grs. troy weight. 

 The brain of the celebrated surgeon Dupuytren 

 weighed 4 Ibs. 10 oz. troy weight. (Both of 

 these eminent individuals, it ought to be re- 

 marked, died with the brain in a state of dis- 

 ease.) The brain of men, with feeble intel- 

 lectual powers, is, on the contrary, often very 

 small, particularly in congenital idiotismus. The 

 brain of an idiot, fifty years old, weighed but 

 1 Ib. 8 oz. 4 dr., and that of another, forty years 

 of age, weighed but lib. 11 oz. 4 dr. 



" 2. The female brain is lighter than that of 

 the male. It varies between 2 Ibs. 8 oz. and 

 3 Ibs. 11 oz. troy. I never found a female 

 brain that weighed 4 Ibs. The brain of a girl, 

 an idiot, sixteen years old, weighed only 1 Ib. 

 6 oz. 1 dr. The female brain weighs, on an 

 average, from four to eight ounces less than 

 that of the male ; and this difference is already 

 perceptible in a new-born child. 



" 3. The brain arrives, on an average, at its 

 full size towards the seventh or eighth year. 

 Soemmering says, erroneously, that the brain 

 does not increase after the third year. Gall 

 and Spurzheim, on the other hand, are of opi- 

 nion that the brain continues to grow till the 

 fourteenth year. The brothers Wenzel have 

 shewn that the brain arrives at its full growth 

 about the seventh year. This is confirmed by 

 Hamilton's researches." 



(The reader will perceive that these state- 

 ments do not exactly accord with the results of 

 Dr.John Reid's observations. It seems probable 

 that the data upon which Tiedemann's conclu- 

 sions were founded have been too limited in 

 number. In calculating the weight of the brain 

 in adolescence and adult age, some allowance 

 should be made for the greater proportion of 

 water at the former period ; the quantities of 

 that fluid being at those ages 72 and 74 parts 

 in 100 respectively, according to L'Heritie.) 



" 4. Desmoulins is of opinion that the brain 

 decreases in old people. From this circum- 

 stance he explains the diminution of the 

 functions of the nervous system and intellec- 

 tual powers. The truth of this assertion has 

 not as yet been determined. The brothers 

 Wenzel, and Hamilton deny it. 



" It is remarkable that the brain of a man, 

 eighty-two years old, was very small, and 

 weighed but 3 Ibs. 2 oz. 3 dr., and the brain of 

 a woman, about eighty years old, weighed but 



* Loc. cit. p. 502. 



