FOODS — HUMAN NUTRITION. 65 



in this respect, even though they may have had ample proteins, fats, and carbo- 

 hydrates. This question merits further investigation. 



" Little is known regarding the form in which calcium exists in food mate- 

 rials, and at present differentiation among the different groups of calcium com- 

 pounds eaten can not be made. Metabolism experiments indicate that a healthy 

 man accustomed to full diet requires about 0.7 gm. of calcium oxid for equilib- 

 rium, but many of the dietaries show less than 0.7 gm. calcium oxid per man 

 per day." 



Some of the European investigators hold that the food should furnish at least 

 from 1 to 1.5 gm. calcium oxid per man per day. If these estimates of the 

 normal requirement and the estimates of the amounts in typical American 

 family dietaries are even approximately correct, it would follow that a con- 

 siderable proportion of American families would be benefited by food richer 

 in calcium compounds than that which they habitually consume. 



In the case of magnesium the data were not sufficient for general deduction. 



" This subject [of calcium metabolism] calls for much more extended study, 

 especially in view of the fact that recent medical observations are tending to 

 show that disturbances of calcium metabolism are connected with a number of 

 abnormal conditions. 



" Experimental dietary studies have shown that it is entirely feasible to in- 

 crease largely the calcium and phosphorus intake by making a more liberal use 

 of milk in the dietary. The same may, of course, be said of the various milk 

 products in which the calcium and phosphorus compounds are largely or wholly 

 retained, such, for example, as cheese, junket, kumiss, buttermilk, or cream. 

 This is probably the simplest and more effective means of improving the dietary 

 as regards calcium and phosphorus compounds, without decreasing its accept- 

 ability or materially increasing its cost and with distinct advantages in other 

 directions." 



Phosphorus in beef animals, I, II, C. K. Francis and P. F. Trowbridge 

 {Jour. Biol. Chem., 7 (1910), No. 6, pp. 481-501; 8 {1910), No. 1, pp. 81-93).— 

 In the first of these studies of the occurrence of phosphorus in animals, 10 

 steers and a cow were used, ranging from an emaciated to a very fat condition 

 when slaughtered. Three of the animals had been fed grain and alfalfa hay 

 2 : 1, the grain consisting of cracked corn, whole oats, and linseed meal 6:3:1. 

 The remaining animals had been fed grain and alfalfa hay 2.5 : 1, the grain 

 mixture consisting of cracked corn and linseed meal 8 : 1. The feeding was 

 continued for varying periods, to suit the experimental conditions. After 

 slaughtering, samples of different cuts were taken for analysis. 



The conclusions which were reached follow : 



"A method which involves heating of the solution before precipitation of the 

 inorganic phosphorus does not yield results which represent the true condition 

 of the soluble forms of phosphorus compounds in cold water extracts of beef. 



" Soluble organic phosphorus compounds existing in beef and in cold water 

 extracts of the same are converted into inorganic forms by heat. 



" The change is practically complete when the temperature is maintained at 

 70° for 15 minutes. 



" From 52 to 65 per cent of the total phosphorus in cold water extracts is in 

 the organic form, but may be reduced to from 9 to 20 per cent if heated to about 

 70°, accompanied by a corresponding increase of the inorganic phosphorus. 



" The round cut of beef contains more phosphorus, in forms which are soluble 

 in cold water, than any of the other cuts. 



" Phosphorus is found chiefly in the muscular or connective tissue, the fats 



contain but little. 



