CH. XXXIX.] 



METABOLIC BALANCE-SHEETS 



587 



The Discharge of Nitrogen. 



In man the minimum daily allowance of nitrogen is 15 grammes, 

 or 0'02 per cent, of the body-weight ; in the carnivora about O'l per 

 cent. ; in the ox, as an instance of a herbivorous animal, 0'005 per 

 cent. In certain races of mankind (e.g. coolies) the nitrogen require- 

 ment is less than in Europeans, and evidence has been recently 

 accumulating to show that even Europeans can maintain equilibrium 

 on diets much scantier than what is usually stated to be the minimum 

 (see p. 460). 



In an animal fed exclusively on flesh, the discharge of nitrogen 

 at first increases pari passu with the absorption of proteid, the 

 absorption of oxygen being proportionately increased at the same 

 time. The animal, however, gains weight from increase of fat, the 

 proteid being split into what is called a nitrogenous moiety, which 

 is burnt off, and a non-nitrogenous moiety which is converted into 

 fat. 



The discharge of nitrogen is not immediately or markedly 

 influenced by muscular work (see p. 555); the increased combustion 

 that occurs in working as compared with resting muscles falls chiefly 

 on their non-nitrogenous constituents. 



Balance of Income and Discharge in Health. 



In Chapter XXVIII. tables are given of adequate diets; these 

 will in our balance-sheets represent the source of income ; the other 

 side of the balance-sheets, the expenditure, consists of the excretions. 



EXCHANGE OF MATERIAL ON AN ADEQUATE DIET 

 (Ranke's table).* 



The above table was constructed from data derived from the observations of 

 Prof. Ranke on himself. Though made many years ago, Ranke's tables still serve 

 as typical and standard examples of metabolic balance-sheets. 



In man the discharge of nitrogen per kilo, of body-weight 

 is 0*21 gramme, and of carbon 3 '03 grammes, the quotient 



