316 NERVOUS SYSTEM. 



of about one ounce during each subsequent decennial period ; 

 thus confirming the opinion, that the brain diminishes in ad- 

 vanced life." 



The comparative weights of the several parts of the en- 

 cephalon, calculated from observations on the brains of fifty- 

 three males and thirty-four females, between the ages of 

 twenty-five and fifty-five, are as follows : 



The proportionate weight of the cerebellum to that of 

 the cerebrum, in the male, is as 1 to 8f, and in the female, 

 as 1 to 8J. 



The specific gravity of the whole encephalon is about 

 1,036, that of the gray matter being 1,034, and of the white, 

 1,040.' 



The above weights are quoted from Quain's admirable 

 work on anatomy, and the normal range of variations and 

 averages only are given. "When we come to treat of the 

 cerebrum and its relations to intelligence, we will discuss 

 the weights of the brain in idiots and in persons of extraor- 

 dinary intellectual power, as far as any data upon these 

 points are to be found. 



Some Points in the Physiological Anatomy of the 

 cephalon and its Connections. The direction of the fibres 

 in the encephalon, their connections with the cells of the 

 gray substance, the course of commissural fibres connecting 

 together the different parts of the gray substance of the cere- 

 brum, the cerebellum, and the deeper ganglia, and finally 

 the avenues of communication between the fibres of the en- 

 cephalon and the cord, are points of exceeding intricacy ; 



1 QUAIN, Elements of Anatomy, London, 1867, vol. ii., p. 568, et seq. 



