COMPOSITION OF THE BRAIN. 



219 



" The action of the voltaic current in the or- 

 gans of the senses in living beings produces pre- 

 cisely the sensations belonging to each of them. 

 By exciting the optic nerves the sensation of 

 light is produced ; and that of sound, if the nerves 

 of the ear are touched." x 



The brain, according to Vauquelin's analysis, is 

 composed of 



Albumen 7.0 



Fatty matter 4.6 



Phosphorus 2.0 



Sulphur, salts, and acids 6.4 



20.0 

 Hydrogen and oxygen in the proportion constituting water 80.0 



1000 



The white substance of the brain and nerves 

 contains nearly seventy-five per cent of water ; the 

 gray about eighty-five per cent. The proportion 

 of water is less in the spinal cord, and still less in 

 the nerves. 



This analysis shows that water constitutes four- 

 fifths of the human brain ; and, as Dr. Hare re- 

 marks, " this is the best account it has hitherto 

 pleased God to enable the brain of man to give 

 of its own constitution." 



The four principal parts into which the en- 

 cephalon is divided are so intimately connected 

 externally and internally by the white nerve-fibres, 

 the white substance consisting of tubular fibres 

 and the gray substance consisting of angular, 



1 Guillemin's Forces of Nature, p. 603. 



