CHEMICAL CHANGES IN HUMAN BRAIN 459 



various parts of the brain. Concerning the extra nuclear proteins 

 (nucleoprotein a) it is difficult to make more than a guess — that 

 they would vary with the other functioning protein (nucleo- 

 protein h). 



Neutral sulphur is a rough measure of the amount of protein 

 metabolism taking place. It is rather striking that the greatest 

 rate of protein metabohsm is in the forebrain (table 2) and cere- 

 bellum (table 8) and least in the brain stem (table 5). The rate 

 in all remains rather constant in spite of the fact that the amount 

 of protein increases with age. 



Throughout growth the total extractives are present in much 

 larger amounts in the cerebellum (table 8) than in the rest of the 

 brain. The stem has a slightly larger percentage than the fore- 

 brain. In all divisions the maximum addition per day is reached 

 at about three months of age (tables 2, 5, and 8, fig. 2). After 

 this there is a slow decrease in amount of daily additions till old 

 age, indicating that aging is a regular decrease in rate of metabo- 

 lism. The larger part of the extractives in the cerebellum is com- 

 posed of inorganic constituents. This is probably to be expected 

 from the larger protein content in this division of the brain. 



The total sulphur increases more rapidly and attains a some- 

 what greater percentage in the brain stem than in the forebrain 

 (table 1) and a considerably greater percentage than in the cere- 

 bellum (table 7). This seems to be largely due to the relatively 

 larger amounts of lipins in each division in the order named. 

 The inorganic sulphates gradually increase in each division at 

 about the same rate. 



The amount of total phosphorus does not differ much in dif- 

 ferent parts of the brain, but the lipin phosphorus is greater in 

 the stem (table 5) and forebrain (table 2) than in the cerebellum 

 (table 8). The inorganic phosphates seem to be closely related 

 to nucleoprotein h, because they are represented to a much greater 

 extent in the cerebellum than in the other divisions of the brain. 



