I9I2] Paul E. Howe 95 



In the case of dogs there is a difference o£ opinion as to the 

 relation between the urea-nitrogen and the total nitrogen. Schön- 

 dorf (22) and others hold that the percentage of urea-nitrogen 

 decreases, while in all of our experiments it has remained nearly 

 constant, which fact, coupled with the failure to find marked quan- 

 tities of organic acids in the urine, would show that dogs are better 

 able to utilize their body Stores. This may be due to the fact that 

 the dog is naturally a "high-protein" animal. 



The daily Creatinine excretion, which is a constant for any indi- 

 vidual under normal conditions of feeding and is generally believed 

 to be a function of the muscular metabolism, decreases gradually 

 as the fast progresses and in correspondence with the decreasing 

 amounit of protoplasm. 



Creatine, which does not occur in normal urines, or is found 

 only in cases associated with muscular disintegration, appears dur- 

 ing fasting and ordinarily becomes a constant constituent. It has 

 recently been shown that the feeding of carbohydrate causes the 

 excretion of creatine to stop (5, 17) ; while ingested fats may even 

 cause an increase in the excretion of this form of nitrogen. In 

 one of our dog experiments (15) there was a disappearance of 

 urinary creatine from the iQth to the 59th fasting days. This phe- 

 nomenon might be explained on the above basis. It is improbable, 

 however, that the body could synthesize sufficient glycogen at this 

 stage of the fast to cause the disappearance of the creatine. The 

 real explanation is therefore not apparent. 



In connection with the repeated fast, previously mentioned, it is 

 interesting to note that the excretions of creatine as well as of total 

 nitrogen were practically the same during each of the two fasts, 

 notwithstanding the fact that the second fast was twice as long as 

 the first. • This would indicate an intimate relation between the 

 total-nitrogen excretion and the quantity of creatine excreted. 



When the data representing the creatine and Creatinine excretions 

 of a fasting animal are examined, it is seen that there is generally a 

 progressive increase in the creatine Output and an accompanying 

 decrease in the Creatinine elimination, until the output of creatine 

 exceeds that of the Creatinine. In other words, when expressed 

 graphically, the curve representing the course of the creatine excre- 



