I9I2] Paul E. Howe 93 



subject prepared for the preliminary examination for the degree of 

 Doctor of Philosophy during a seven-day fast. 



The fasting State is indicated in the body by certain changes; 

 such as a general decrease in the body metaboHsm, represented by 

 variations in the nitrogen excretion and the respiratory exchange, a 

 decrease in the fat and glycogen Stores, a decrease in the volume of 

 muscle and in the size and weight of certain organs. The tempera- 

 ture remains normal, for a time at least, but shows a tendency to 

 decrease toward the end of the fast. 



The decrease in the general metaboHsm is well Illustrated by the 

 data obtained from the respiration calorimeter experiments. It has 

 been shown by the earlier investigators and more recently by Bene- 

 dict (2) that, in a well fed man, the quantities of protein and fat 

 which were utiHzed, and the energy change (calories) per day, 

 decreased very gradually and tended toward a constant minimum. 

 In addition to the excreted carbon dioxide, Benedict determined the 

 amount of oxygen consumed. From these data it was shown that 

 the glycogen consumption, which is most rapid on the first day, 

 decreases as the fast progresses. It is probable that the glycogen 

 Store is never depleted and that even in fasting there is a resynthesis 

 of glycogen from the protein material present in the body. 



Decreased metaboHsm in fasting is also shown by the quantities 

 of nitrogen-containing substances eliminated in the excreta. We are 

 particularly concerned with the losses of nitrogen, for it is the 

 protein material which is the most fundamental nutritive substance 

 and which the body strives to protect. In fasting, the nitrogen- 

 containing substances in the urine or feces arise from the tissues and 

 hence the total nitrogen excretion is a measure of the quantity of 

 muscular or organ tissue catabolized. The excretion of total nitro- 

 gen in the urine decreases rapidly at the beginning of the fast and 

 soon reaches a minimum, which is maintained for some time. This 

 minimum of nitrogen excretion, representing a minimum protein 

 disintegration, is Held to represent the " maintenance " metaboHsm 

 of the individual, i. e., that amount of protein substance which if 

 supplied, with sufficient fats or carbohydrates, in the form of food 

 would sustain life. This minimum has variously been shown to be 

 greater or less than the metaboHsm as represented by fasting ex- 

 periments. 



