PERCENTAGE OF WATER 



increasing brain weight; a fact already demonstrated 

 previous tables and charts. 



133 



by the 



WEIGHT OF WATER 

 17 r GMS. 



CONSTANT PERCENTAGE 

 BRAIN 



WEIGHT OF WATER 



BRAIN 



ALBINO RAT 



ACCORDING TO BRAIN WEIGHT 



FEMALE 



BRAIN WEIGHT GMS. 



BODY WEIGHT GMS. 

 AGE IN DAYS 



1.7 1.8 



I 

 ) 200 



i MALE 



1.9 



Chart 4 



To show the absolute increase in the weight of water corresponding to the 

 increase in brain weight. The data for the two sexes plotted separately. The 

 first entry is for a brain weight of 0.35 grams. Below are given the body weights 

 and the ages in days for the several brain weights. The dotted line indicates 

 the amount of water which would be required to maintain the percentage at the 

 initial value. 



Second. The increments of brain weight are characterized by 

 a continuous though small diminution in the percentage of water 

 in the successive increments, the more rapid diminution occur- 

 ring after the first fifteen days of life. 



Third. After the rat has attained about fifteen days of 

 age, the percentage of water in the increment of weight becomes 



