446 



METABOLISM, NUTRITION, AND DIET 



excreted is about twenty to thirty grams. This quantity enters the body in 

 the food, chiefly in combination with complex compounds. It is a question 

 as to what per cent, of organic salts, like the calcium, the phosphates, and 

 the iron, is available when taken into the body in inorganic form. 



We have discussed in previous chapters the role of certain salts in their 

 influence on metabolism; for example, of sodium, potassium, calcium, iron, 

 etc. Foods like milk and eggs are especially rich in calcium and phosphorus 

 and are particularly desirable for young children, the former for its influence 

 on the growth of the skeleton, the latter for the same reason and as a stimu- 

 lator of growth of protoplasm in general. Lack of mineral constituents, 

 especially calcium compounds, in food shows its influence on metabolism 

 in the disease known as rickets. 



Numerous investigations are in progress which may demonstrate more 

 fully the specific influence of phosphorus on animal nutrition and on 

 growth. Tunnicliff has demonstrated that an increase of the phosphorus 



NUTRITION EXPERIMENT IN FIVE-MONTHS-OLD PIGS. (E. B. FORBES.) 



Rations. 



Per cent, gain 



in live 



weight in 



60 days' 



feeding. 



Hominy ; blood flour ; bran extract. I 69.1 



(Phosphorus mostly as phytin.)j 

 Hominy; blood flour; bone flour.! 61.0 



(Phosphorus mostly as tricalcic 



phosphate). 

 Hominy; blood flour. (Low phos- 41.6 



phorus ration). 



Per cent, gain in certain 

 tissues corresponding to 

 i per cent, gain in live 

 weight. 



Psoas 

 muscle. 



.81 



.61 



Ash of 



humer- 



us. 



59 

 .72 



.08 



Thick- 

 ness of 

 back fat. 



.64 

 .82 



i .04 



content of the food of children, if given in complex organic form, increases 

 the efficiency of the metabolism of nitrogen by as much as 10 per cent. 

 If given to children as calcium phosphate it has no beneficial influence 

 in this regard. Forbes, in his experiments on the nutrition of pigs, shows 

 that the individuals fed with food to which phosphorus was added, as ground 

 fresh bone, grew larger and stronger skeletons, but that the presence of 

 organic phosphorous (phytin) led to the greatest general growth. 



