FOODS 



119 



constituent and their amounts determined. The absorption apparatus is 

 again weighed. The increase in weight represents the amounts of water 

 and carbon dioxid eliminated and absorbed. The animal is again weighed 

 and the loss in weight noted. 



If at the same time it is desired to collect the heat dissipated from the 

 body it is necessary to surround the animal chamber with a water jacket, the 

 rise in temperature of which, expressed in calories, indicates the amount of 

 heat dissipated and collected. Since an apparatus of this character de- 

 termines the extent of the respiratory exchange as well as the amount of 

 heat dissipated, it is termed a Respiration Calorimeter. 



For long-continued experiments on animals of large size and on man, 

 one of the larger and more accurately constructed forms of apparatus, such 

 as Benedict's (see Chapter on Animal Heat) must be employed. 



In an experiment to determine the extent of the metabolism during a 

 fasting period there was collected on the first and second days 12.17 an d 

 12.84 grams of nitrogen and 188.5 an d I 79-4 grams of carbon respectively. 

 From these amounts it was calculated that 76.1 and 80.3 grams of protein 

 and 206.1 and 191.6 grams of fat respectively were metabolized. From these 

 figures it is evident that at least equal amounts of protein and fat must be 

 consumed. As a matter of fact, however, these amounts would be insufficient 

 to maintain the energy equilibrium of the body. It has been estimated that 

 at least from 10 to 14 per cent, more food must be added. 



In an experiment, made by Vierordt on the customary diet the following 

 results, somewhat rearranged were obtained. On the right, under the term 

 outcome, are arranged the amounts of the substances eliminated; on the left, 

 under the term income, the amounts of the food and tissue principles which 

 were calculated to have been metabolized. If the body is to retain its usual 

 weight it is evident that equivalent amounts of these food principles must be 

 introduced into the body. 



COMPARISON OF THE INCOME AND OUTCOME 



In the foregoing experiment the total nitrogen contained in the urine 

 which was 15.8 grams is expressed in the table in terms of urea. The chemic 

 composition of urea, COH 4 N 2 taken in connection with the amount stated, 

 indicates that it is the chief end-product of protein metabolism; and as i 

 gram of nitrogen corresponds to 2.14 grams of urea and either to 6.25 grams 

 of protein it is apparent that the urinary nitrogen corresponds to 98.80^ grams 

 of protein metabolized. The feces, however, contained 3.3 grams of nitrogen 

 corresponding to 20.62 grams of protein, making a total approximately of 

 120 grams of protein. From this it is apparent that an equal amount of 



