OF THE NERVOUS MATTER. 175 



differs entirely, both from that of ordinary fats and of 

 the compounds of proteine. Common fats contain no 

 nitrogen, while the compounds of proteine contain nearly 

 17 per cent. Leaving the phosphorus out of view, the 

 composition of this acid approaches most nearly to .that 

 of choleic acid, although these two compounds are quite 

 distinct. 



91. Brain and nervous matter is, at all events, formed 

 in a manner similar to that in which bile is produced ; 

 either by the separation of a highly nitrogenized com- 

 pound from the elements of blood, or by the combina- 

 tion of a nitrogenized product of the vital process with a 

 non-azotized compound (probably, a fatty body). All 

 that has been said in the preceding pages on the various 

 possible ways by which the bile might be supposed to be 

 formed, all the conclusions which we attained in regard 

 to the cooperation of azotized and non-azotized ele- 

 ments of food, may be applied with equal justice and 

 equal probability to the formation and production of the 

 nervous substance. 



We must not forget, that, in whatever light we may 

 view the vital operations, the production of nervous 

 matter from blood presupposes a change in the compo- 

 sition and qualities of the constituents of blood. That 

 such a change occurs is as certain as that the existence 

 of the nervous matter cannot be denied. In this sense, 

 we must assume, that from a compound of proteine may 

 be formed a first, second, third, &c., product, before a 

 certain number of its elements can become constituents 

 of the nervous matter ; and it must be considered as 



