METABOLISM, NUTRITION AND DIETETICS 475 



quantity of iron in a number of actual dietaries, finds that 

 it only amounts to about 8 to 10 milligrammes a day. He 

 concludes that the greater part of it must be retained in the 

 body and used over and over again. 



Milk is poor in iron, but this does not hinder the develop- 

 ment of the young child, except when it is weaned too late, 

 when it is apt to become anaemic, unless the milk is supple- 

 mented with a food rich in iron, such as yolk of egg. The 

 explanation is that the foetus, especially in the last three 

 months of intra-uterine life, accumulates a store of iron in 

 the liver and other organs ; so that, in proportion to its 

 body-weight, it is at birth several times richer in iron than 

 the adult. This iron, of course, all comes from the mother, 

 and the loss is not exactly balanced by the excess of iron in 

 her food ; certain of her organs, the spleen, for instance, 

 though not apparently the liver, are impoverished as regards 

 their content of iron. 



(4) Dietetics. There are two ways in which we can 

 arrive at a knowledge of the amount of the various food 

 substances necessary for an average man : (a) By consider- 

 ing the diet of large numbers of people doing fairly definite 

 work, and sufficiently, but not extravagantly, fed e.g., 

 soldiers, gangs of navvies, or plantation labourers ; (6) by 

 making special experiments on one or more individuals. 



Voit, bringing together a large number of observations, 

 concluded that an 'average workman,' weighing 70 to 75 

 kilos, and working ten hours a day, required in the twenty- 

 four hours 118 grammes proteid, 56 grammes fat, and 500 

 grammes carbo-hydrate, corresponding to about 18*3 grammes 

 nitrogen and at least 328 grammes carbon. 



Ranke found the following a sufficient diet for himself, 

 with a body-weight of 74 kilos : 



Proteids - loo grammes. 



Fat --. - 100 



Carbo-hydrates - 240 



This corresponds to only 14 grammes nitrogen and, say, 

 230 grammes carbon. 

 A German soldier in the field receives on the average 



Proteids - - -151 grammes. 

 Fat - - 46 



Carbo-hydrates - - 522 



