456 FOOD. [CH. xxvin. 



the chief, are simultaneously liberated. During muscular exercise 

 the output of carbon greatly increases ; the increased excretion 

 of nitrogen is not nearly so marked. Taking, then, the state of 

 moderate exercise, it is necessary that the waste of the tissues 

 should be replaced by fresh material in the form of food; and the 

 proportion of carbon to nitrogen should be the same as in the 

 excretions: 250 to 15, or i6'6 to i. The proportion of carbon 

 to nitrogen in proteid is, however, 53 to 15, or 3-5 to i. The 

 extra supply of carbon must come from non-nitrogenous food 

 viz. fat and carbohydrate. 



Moleschott gives the following daily diet : 



Proteid laogrms. 



Fat 90 



Carbohydrate 333 



Ranke's diet closely resembles Moleschott's ; it is 



Proteid 100 grms. 



Fat loo 



Carbohydrate 250 



Such typical di.ets as these must not be considered as more 

 than rough averages of what is necessary for a man in the 

 course of the day. Actual experience shows that in the diets 

 of different nations there are considerable variations from this 

 standard without the production of ill effects. Age, and the 

 amount of work done also influence the amount of food neces- 

 sary ; growing children, for instance, require a relatively rich 

 diet ; thus, milk, the diet of the infant, is proportionally twice 

 as rich in proteids, and half as rich again in fats, as the normal 

 diet given above. During work more food is necessary than 

 during inactivity. 



Ranke's and Moleschott's diets just given are by no means 

 generous ones ; most English people take more proteid. From 

 the composition of the more commonly-used foods, G. N. Stewart 

 calculates that 500 grammes of bread and 250 grammes of lean 

 meat constitute a fair quantity for a man fit for hard work. 

 Adding 500 grammes of milk, 75 grammes of oatmeal porridge, 

 30 grammes of butter, and 450 grammes of potatoes, we get, 

 approximately, 20 grammes of nitrogen and 300 grammes of 

 carbon contained in 135 grammes of proteid, 97 grammes of fat, 

 and about 400 grammes, of carbohydrate. This diet is thus a 

 more liberal one than the " adequate " diets just given. 



