STATISTICS OF NUTRITION. 673 



and in the urine and feces it may be determined whether there is an 

 increase or a waste of the nitrogenous matter (albuminoids) of the 

 economy. 



3. The nitrogen in the urine is a measure of the decomposition of 

 albuminoids in the body, while from the sum of the amounts of nitrogen 

 in urine and faeces may be deduced the amount of albuminoids which 

 become fixed in the body. 



4. The difference in amount of carbon in income and outgo (including 

 that which is given off by lungs and skin), taking into account the 

 carbon derived from decomposition of albuminoids, gives us a means of 

 estimating the changes in the fat of the animal body, since with the 

 exception of fat there is not, in any important amount, any other carbon 

 compound in the body. 



5. Differences in the amount of water in the economy are readily 

 calculated. It is onl}- necessary to compare the increase or decrease of 

 body weight with the data determined as to the decomposition of albumen 

 and fat. 



For making the above estimates the composition of albumen is 

 placed as follows : — 



c. h. n. o. s. 



53.6 per cent. 7.0 per cent. 16.0 per cent. 23.0 per cent. 1.0 per cent. 



Albumen thus consisting of 16 per cent, of nitrogen, if the amount 

 of nitrogen in the urine is multiplied by 6.25 (= W -) we are able to 

 determine the amount of albumen represented by the nitrogen in the 

 urine. 



As regards the fats, all the animal fats are remarkably constant in 

 their composition ; they possess in mean 76.50 per cent, carbon. 



Prom the difference in carbon in income and outgo the amount of 

 carbon of the decomposed albumen is first deducted (53.6 per cent.), 

 and from the remainder by multiplication by the factor 1 .301 (= jv.gjj) the 

 amount of fat may be calculated. 



The behavior of the mineral constituents is calculated from the 

 mineral constituents of the food and that of the urine and fasces. So, 

 also, for water in a like manner. 



The following example (quoted by Schmidt-Mulheim, who has been 

 largely followed in this chapter) makes clear the method by which such 

 statistics of nutrition are reached : — 



Henneberg fed a full-grown ox, weight 712.5 kilos, for twenty -eight 

 clays with 5 kilos clover-hay, 6 kilos oat-straw, 3.7 kilos crushed beans, 

 0.06 kilo salt, and 56.1 kilos water. During the experiment the animal 

 increased daily 1.035 kilos in weight. 



From the analysis of the food, faeces, and urine, and from the esti- 



43 



