144 



PHYSIOLOGY 



low that it could not be accurately determined. A series of 

 observations is given in table 98. 



TABLE 98 



Disappearance of glycogen after feeding. Normal young albino rats. (Cramer 



and Lochhead, '18) 



A study of the nitrogen excretion has been made by Hatai 

 ('05); Chicago colony : Ration "Uneeda Biscuit" arid water- 

 table 99. 



From observations on 89 male rats at different ages and weights as in 

 table 99, the following results were obtained : 



1. The total amount of urine increases with the weight up to 120 

 grams, then decreases very decidedly. From 180 grams it again in- 

 creases up to 220 grams, beyond which weight it remains rather constant. 

 A diminution of urine in animals between 120 and 180 grams, or ap- 

 proximately 70-125 days old, seems to be a normal phenomenon rather 

 than mere statistical variation. Whether or not this is a phenomenon 

 of adolescence needs further investigation. It must be noted, however, 

 that puberty in the rat begins at about seventy days after birth. The 

 smaller animals excrete a relatively greater quantity of urine than the 

 larger animals. 



2. The total amount of nitrogen is quite independent of the amount 

 of urine, and increases constantly and continuously throughout life. 

 The smaller rats, however, excrete a relatively greater quantity than the 

 larger animals. 



3. The percentage value of urinary nitrogen is 91 per cent of the 

 total in the case of smaller animals, and 89 per cent in the case of the 

 larger. 



