6 PHYSIOLOGY CHAP< 



estimation of the total consumption of protein, we confine 

 ourselves to determining the total amount of nitrogen in the 

 excreta by Kjeldahl's method, and pay no attention to the 

 ulphur and phosphorus. If we multiply the nitrogen by 6'25 

 we can calculate, as we have already seen, the sum total of 

 protein consumed. 



In order to estimate the total consumption of non-nitrogenous 

 stances, fats and carbohydrates, we may confine ourselves to 

 determining the total amount of carbon in the excreta. Since 

 e proportion of nitrogen to carbon in protein is as 16 to 52'8 

 we can easily calculate the carbon in the protein consumed and 

 obtain by subtraction the carbon resulting from the decomposition 

 t tne non-nitrogenous organic substances 



In order to complete the list of materials taken in and 

 discharged, and obtain a balance of account, we must not only 

 -nalyse the food urine and faeces, but also determine, at least 



H ,, f x re en absorbed > 1 carbon 



and water discharged, by the lungs and skin 



The carbon dioxide only is determined directly 

 h from the lungs only are 





