METABOLIC ACTIVITY OF NERVOUS SYSTEM 



407 



TABLE 2 

 Percentage of water in the brain 



PERCENTAGE OF WATER IN THE BRAIN 



It is conceivable that following the greater or less accumula- 

 tion of the metabolic products in the brain, the water content 

 might show a change also. We have determined the amount 

 of water in the brain of the control and test rats and found 

 that while their average observed values are identical, both 

 being 78.6 per cent (tables 1 and 2, 'Observed'), yet their 

 successive differences during the twenty-three hours after star- 

 vation are not identical, but show interesting deviations. In 

 dealing with the values on the percentage of water, we must 

 consider, in the interest of precision, the influence of brain size 

 on the water content. 



Donaldson ('16) finds that although the percentage of water 

 in the brain is a function of age, nevertheless, within the same 

 age, the heavier brain gives relatively less water than the lighter 

 brain, and vice versa. 



Since, then, the brain weights given by both the control and 

 test rats are not identical, we thought it advisable to transform 

 the observed values of the percentage of water to the theoretical 



