FORBES: MINERAL ELEMENTS IN NUTRITION 439 



nitrogen and sulphur liberally in each period, though, naturally, 

 less of these elements was stored from the ration of corn alone 

 than from rations containing more protein. 



Potassium was stored in all periods except one; strange to 

 say, the ration composed of rice polish and wheat bran was the 

 one in which this element was supplied in the greatest amount. 

 Animals have no means of storage of large amounts of potassium 

 salts. The large excretion of potassium on this maximum in- 

 take may be considered as a protective measure. In this case 

 the negative balance did not signify insufficiency. 



Sodium and chlorine balances were much affected by the water 

 drunk. The intake of these elements would have been insuffi- 

 cient had not the amounts present in the foods been supplemented 

 by the use of salt. Those individuals which drank the least 

 water retained the most sodium and chlorine. 



The more significant results of this experiment have to do 

 with calcium, magnesium, and phosphorus. These elements are 

 closely associated in metabolism. In the two rations where the 

 corn was supplemented by skim milk and by tankage (contain- 

 ing a considerable amount of bone scrap) the calcium retention 

 was 9 to 10 times as great as in any of the rations composed of 

 grains and other seeds and seed products. On rations of corn 

 alone, of corn and soy beans, and of rice polish and wheat bran 

 the calcium balances were negative; that is, more calcium was 

 given off* in excreta than was received in the food. This result 

 emphasizes the fact that the cereals are very poor bone-foods. 

 The negative calcium balances from the ration of corn and soy 

 beans call attention to the fact that the phenomenally high cal- 

 cium content of legumes is true of the plants as a whole and not 

 of the seeds. This emphasizes the value of leguminous rough- 

 age as bone-food. 



In these rations the retention of calcium was closely related 

 to the intake of the same, and not appreciably affected by the 

 excess of mineral acid. Physiologically, calcium and magnesium 

 are balanced opposites. An excess of magnesium in the blood 

 causes a counter-active liberation of calcium; but the propor- 

 tion of these elements in the blood does not follow closely their 



