452 Influence of Inanition on Metabolism. 



by a carbon dioxide liberation on the computation of the protein, fat, and 

 carbohydrate by means of the method of simultaneous equations might be very 

 complex. One serious objection to this method of computation is that the possi- 

 bilities of intermediary metabolism are not considered in any way, since only 

 the end products of metabolism are used for obtaining the data. It is believed, 

 however, that acidosis did not proceed to any such degree in these experiments 

 as to depreciate materially the accuracy of the computations of the protein, 

 fat, and glycogen katabolized. 



BODY MATERIALS KATABOLIZED. 



The measurement of the end products of katabolism appearing in the respira- 

 tory gases and the urine furnishes the necessary data for determining the 

 nature of the total katabolism. Aside from the interpretations of the nitrogen 

 output and more specifically the recent emphasis laid upon the interpretation 

 of the partition of the nitrogen in the urine, deductions from the respiratory 

 quotient have been of greater value in indicating the nature of the total 

 katabolism than have those from any other measured factor. But while the 

 respiratory quotient is an admirable index of katabolism in short experiments 

 in which the body is at absolute rest, provided that the body material has not 

 previously been heavily drawn upon as a result of a protracted period of fast- 

 ing, knowledge of the katabolic processes during inanition has been so defi- 

 cient that the usual method of employing the respiratory exchange as an index 

 of katabolism during a prolonged fast is hardly justified. In nearly all the 

 studies of the respiratory exchange that have thus far been made, the so-called 

 " michternwert " is of fundamental importance. It is necessary, however, in 

 considering experiments of the nature of these here reported, to bear in mind 

 that, even after 12 hours' fast, there may still be a considerable absorption from 

 the intestine of food or at least of partially digested material. So long as 

 this absorption is uniform, it introduces no material error into the determina- 

 tion of the fasting value, since its effect is measured along with the effect of 

 the continued protein katabolism. The ingestion of even small amounts of 

 food produces immediately very considerable changes in the respiratory ex- 

 change, and since in all experiments of short duration, the differential method 

 is emplo} r ed, it is important in studying factors influencing metabolism such as 

 the ingestion of food and muscular work, that the respiratory exchange be 

 measured prior to the ingestion of food or the beginning of muscular exercise. 

 Hence, the value of the respiratory exchange, when the body is at absolute rest 

 after a period of 12 hours without food, is usually taken as the basis for 

 comparison. The differences, then, between the respiratory exchange during 

 rest and that of the changed condition of the experiment indicate the effect of 

 the change. The respiratory quotients obtained in the fasting experiments 

 here reported, on the other hand, represent the resultant value of all the oxy- 

 gen absorption and the total carbon dioxide production of each 24 hours. 



