STARVATION 569 



comparing the creatine and creatinine output with that of nitrogen to 

 determine whether all of the nitrogen liberated by the breakdown of 

 muscle has been excreted, or whether some has been retained either for 

 resynthesis in the muscle itself or for use elsewhere. If the muscle 

 breakdown as calculated from the creatine-creatinine output is greater 

 than that calculated from the nitrogen, synthesis of the noncreatine 

 remainder must be occurring ; whereas if the breakdown calculated from 

 nitrogen is greater than that calculated from creatine, etc., other tis- 

 sues than muscle must be contributory. Stored nitrogen or free nitro- 

 gen in transit from tissue to tissue for utilization is the most likely 

 source of such excess nitrogen. 



That transference of nitrogenous substances from place to place in the 

 body in starvation is proved (1) by the constant presence of amino ni- 

 trogen in the blood and tissues (Van Slyke) ; and (2) by the effect of 

 copious water drinking. The latter causes a decided increase in the out- 

 put of nitrogen, but it does not appear that the extra nitrogen is due to 

 increased protein breakdown. It is probable, however, that in such cases 

 there would also be an increase in endogenous protein metabolism, since 

 the washed-out free nitrogen would have to be replaced. 



Excretion of Purines. Although at first they fall somewhat, the total 

 amount increases as the fast progresses. Perhaps the first decline is 

 due to general using up of hypoxanthine of muscle and the later rise 

 to the breakdown of nuclei (page 638). 



Excretion of Sulphur. It is important to compare the excretion of 

 sulphur and nitrogen. In the early days of starvation a ratio of 17 N : 1 S 

 has been found, but later one of 14.5: 1, which is practically the same 

 as that in muscle (i.e., 14; 1), indicating that late in fasting the main 

 source of protein supply is muscle. 



Several of the changes observed during starvation can be attributed 

 to the condition of acidosis which supervenes. The acids are derived 

 from incomplete combustion of fat (see page 683), and are represented 

 by ^-oxybutyric, the amount being sometimes considerable (10-15 grams 

 a day), especially in obese individuals. The large ammonia excretion 

 (sometimes 2 grams a day) is evidently for the purpose of neutralizing 

 the excess of acid. Another consequence of the acidosis is the decline 

 in the alveolar tension of C0 2 (page 354), and it is possible that some of 

 the circulatory changes shown in the chart may also be dependent on 

 it. The method of repeated fasting used for reducing obesity is quite 

 safe if the acidosis is carefully watched. 



Many secondary changes also occur in the starving organism. Thus, 

 the mobilization of fat is often responsible for a pronounced increase in 

 the fat content of the blood (see page 698), and that of protein explains 



