Katabolism or Fat. 461 



It appears clearly established that there is a marked diminution in the size of 

 the liver 149 and pancreas as well as other glandular organs, and in all proba- 

 bility these organs are drawn uporj to a considerable extent to furnish the 

 protein for katabolism. Since they rapidly regain their original size on the 

 ingestion of food, it is probable that the fluid of the cell rather than the 

 organized cell proteid is the portion drawn upon. 



KATABOLISM OF FAT. 



It has been customary in all experiments in which the katabolism of fasting 

 man has been measured, to assume that the total fasting metabolism was sus- 

 tained by the katabolism of protein and fat. The amounts of these compounds 

 katabolized by a man at rest were computed from analyses of the respiratory 

 products and the urinary nitrogen. The total protein katabolism was com- 

 puted from the nitrogen excreted in the urine and the amount of carbon in the 

 protein was calculated from the weight of protein katabolized. The carbon 

 from protein was deducted from that of the carbon dioxide and the carbon in 

 the urine, and the remainder was considered to have resulted from the kata- 

 bolism of fat. This procedure has been common in the calculation of all meta- 

 bolism experiments up to the publication of the direct determination of oxygen 

 in some of the Middletown experiments. 150 With the direct determination of 

 oxygen, the data are available for computing by means of simultaneous equa- 

 tions (see p. 38) the quantities of protein, fat, and carbohydrate katabolized. 

 The amounts of fat katabolized per day and per kilogram of body-weight in 

 fasting experiments have been computed and are recorded in table 227. 



In all cases there was a material draft upon body fat which was never less 

 than 106.6 grams per day. On one day 203.6 grams were katabolized. The 

 amounts for the first day of fasting ranged from 106.6 to 156.2 grams, and 

 averaged 135.1 grams. The katabolism per kilogram of body-weight averaged 

 2.10 grams. 



In all but one instance, more fat was katabolized on the second day of the 

 fast, the average amount for the 14 experiments being 165.9 grams or 2.61 

 grams per kilogram of body-weight. The amounts for the third day were by 

 no means as regular as might be expected, the quantities ranging from 183.4 

 grams in experiment No. 59 to 137.7 grams in experiment No. 77. On the 

 basis of per kilogram of body-weight, the range was from 2.80 to 2.25 grams. 

 The average fat katabolism of the 6 experiments was 155.2 grams, somewhat 

 less than the average for the second day of all the experiments. The average 

 amount on the fourth and fifth days was about 147 grams, and on the sixth and 

 seventh days about 15 grams less per day. The largest averages, per kilogram 

 of body-weight, are found on the second and fifth days, while on the first and 

 sixth days, the smallest amounts appear. The minimum katabolism per kilo 



148 Possibly due to depletion of the store of glycogen. 

 150 U. S. Dept. Agr., Office of Expt. Sta. Bui. 175 (1907). 



