.METABOLISM. 5Q1 



the isodynamic principle of foods that have the same caloric value. 

 It suffices tojfurnish the organism with a sufficient number of calories, 

 provided three conditions are fulfilled: 2 (1) It is necessary to 

 determine the digestibility of the food, for only the absorbed foods 

 furnish the energy ; (2) it is necessary to count the need of a minimum 

 of nitrogen; (3) the quantity of food ingested should not exceed the 

 digestive capacity and cause trouble. A man cannot live exclusively 

 on meat, for after many days there will be vomiting and diarrhoea; a 

 man cannot eat potatoes alone, for the quantity ingested would be such 

 that the digestive tract would not tolerate it. Suppose it is necessary 

 to give a diet which will furnish 2,700 calories, and as one-tenth will 

 not be absorbed, we will have to furnish a food whose caloric value is 

 3,000. In giving him 100 grams of proteids we will satisfy greatly his 

 need of nitrogen; these 100 grams correspond to 410 calories. Still 

 we need 2,599 calories, which we can furnish by 278 grams of fat or 

 632 grams of carbohydrates, or a convenient mixture of fats and 

 carbohydrates. 



In determining the proportion of fats and carbohydrates we must 

 note the following facts : ( 1 ) The digestive tract does not work well 

 with large doses of fats, it supports better carbohydrates; (2) on the 

 other hand, the carbohydrates are less costly than fats. Hence it is 

 practically advantageous to diminish the quantity of fats and increase 

 the carbohydrates. In practice we usually take one gram of fat to ten 

 grams of carbohydrates in the food of poor people, and one gram of 

 fat to five grams of carbohydrates in the diet of wealthy people. 

 Hence to furnish the 2,700 calories demanded we would use the 

 following diet : 



100 gr. proteids 410.0 calories. 



55 gr. fats 511.5 



507 gr. carbohydrates 2078.7 



3000.2 (ABTHUS.) 

 Loss of 10 per cent 300.0 



2700.2 



Dr. W. S. HalFs balance sheet for man at light work is as 

 follows:- Income 



in calories. 



Proteids 110 grams x 4100 451,000 



Fat 100 grams x 9400 940,000 



Carbohydrates 400 grams x 4180 1,672,000 



2 Arthus : "Elements de Physiologic," 1905. 



3,063,000 



