572 "WEIGHT OF THE BBAIN AND SPINAL COED. 



From this it appears that the proportionate weight of the cerebellum to that of the 

 cerebrum is, in the male, as 1 to 8f, and in the female as 1 to 8j. The cerebellum 

 attains its maximum weight from the twenty -fifth to the fortieth year ; but the increase 

 in weight after the fourteenth year is shown to be relatively greater in the female than 

 in the male. The whole cerebellum apart from the pons and medulla is heavier in the 

 male ; the lateral lobes of the cerebellum are also heavier in the male. In the male 

 the vermiform process increases gradually from the twentieth to the fiftieth year ; in 

 the female it remains stationary during that period, and after the fiftieth year 

 diminishes rapidly. 



In the new-born infant the ratio of the weight of the cerebellum to that of the whole 

 brain is strikingly different from that observed in the adult, being, according to 

 Chaussier, between 1 to 13 and 1 to 26 ; by Cruveilhier it was found to be 1 to 20. 

 Huschke found the weight of the cerebellum, medulla oblongata, and pons together 

 in the new-born infant, as compared with that of the brain, to be in the proportion of 

 1 to 15, and 1 to 13. In the adult, the proportions were 1 to 7, and 1 to 6. 



In most mammalia, the cerebellum is found to be heavier in proportion to the 

 cerebrum, than it is in the human subject ; in other words, the cerebrum in man is 

 larger in proportion to the cerebellum. 



Soemmerring pointed out the fact that the brain is larger in proportion to the 

 nerves connected with it in man than in the lower animals. 



A comparison of the width of the cerebrum with that of the medulla oblongata 

 shows that the proportionate diameter of the brain to that of the medulla oblongata 

 is greater in man than in any animal, except the dolphin, in which creature, however, 

 it must be remembered that the cerebral lobes exhibit a disproportionate lateral 

 development. The width of the cerebrum in man, as compared with that of the 

 medulla oblongata at its base or broadest part, is about 7 to 1, while in many quadru- 

 l eds it is as 3 to 1 or even as 2 to 1. 



WEIGHT OF THE SPINAL CORD. 



Divested of its membranes and nerves, the spinal cord in the human subject weighs 

 from 1 oz. to 1| oz, and therefore its proportion to the encephalon is about 1 to 33. 

 Meckel states it as 1 to 40. 



The disproportion between the brain and the spinal cord becomes less and less in 

 the descending scale of vertebrata, until at length, in cold-blooded animals, the 

 spinal cord becomes heavier than the brain. Thus, in the mouse, the weight of 

 the brain, in proportion to that of the spinal cord, is as 4 to 1 ; in the pigeon, as 3| 

 t) 1 ; in the newt only as to 1 ; and in the lamprey, as ^ to 1. 



In comparison with the size of the body, the spinal cord in man may be stated in 

 general terms to be much smaller than it is in animals. In regard to the cold- 

 blooded animals, to birds, and to small mammalia, this has been actually demonstrated, 

 but not in reference to the larger mammalia. 



R. Wagner states, as follows, the proportion of the weight of the spinal marrow 

 taken as 1 to the encephalon and its parts 



a, to the nerve roots 



b, to the medulla and pons 



c, to the cerebellum 



d, to the cerebrum 



e, to the encephalon 



1 : 0-53 



1 : 1* 



1 : 5-18 



1 : 42-78 



1 : 48-96 



SPECIFIC GRAVITY OF THE ENCEPHALON. 



The specific gravity of different parts of the encephalon has of late attracted some 

 attention from its having been observed that it varies to some extent in different 

 kinds of disease. From the researches of Bucknill, Sankey, Aitken, and Peacock, it 

 appears that the average specific gravity of the whole encephalon is about 1036, that 

 of the grey matter 1034, and that of the white 1040. There are also considerable 

 differences in the specific gravity of some of the internal parts. (William Aitken, 

 " The Science and Practice of Medicine," 1865, vol. 2, p. 265 : J. C. Bucknill in " The 

 Lancet," 1852 : Sankey, in the "Brit, and For. Med. Chir. Eeview," 1853 : Thos. B. 

 Peacock, in the Trans, of the Patliol. Soc. of London, 1861-2.) 



