Nutrition Studies. 65 



HowelP states that the mineral salts of the body direct its metab- 

 olism, tho iu what manner is not known. The blood serum is rich 

 in common salt and other salts oi' sodium, while the red blood cor- 

 puscles are rich in potassium compounds. The nervous system and 

 the nuclei of all cells are rich in phosphorus, and the skeleton is 

 composed largely of calcium or lime, combined with phosphorus. 

 The power of the blood to carry oxygen is due to hemoglobin, an 

 iron-protein compound in the red corpuscles. Blood deprived of 

 its calcium does not coagulate or clot. In the stomach the pepsin 

 acts only in the presence of an acid, normally hydrochloric, de- 

 rived from the salts of this acid present in the circulation. It is 

 probable that the animal organism is, by reason of its perfection, 

 able to use many of these mineral substances over and over again 

 for tlie same functions, taking them back into the circulation after 

 they have once been used. In spite of this frugal economy, how- 

 ever, losses of mineral matter from the body constantly occur, even 

 during starvation. Ordinarily the rations of farm animals eon- 

 tain all the necessary mineral matters in small quantities, and since 

 the body retains these witli great tenacity when the supply is 

 meager, these small amounts usually suffice. Common salt, lime, 

 and phosphorus are often needed in such large amounts that they 

 may fall short in certain rations, and hence must be added if nor- 

 mal results are to be obtained. 



Appendix Table V sets forth the mineral constituents of feeding 

 stuffs so far as it has been possible to secure them. 



89. Lime and phosphorus. — Large amounts of lime are deposited 

 in the bones of animals, chiefly as phosphate and in smaller amount 

 as carbonate. It is not surprising, therefore, that a long-continued 

 lack of lime and phosphorus in the food is harmful to the skeleton. 



Hart, McCollum, and Humphrey of the Wisconsin Station- have 

 shown that the animal skeleton acts as a reserve storehouse of min- 

 eral matter, doling out lime, phosphorus, etc., when the supply in 

 the food is below requirements, in order that the metabolic pro- 

 cesses of the body may be maintained. Under such conditions the 

 lime and phosphorus content of the flesh and other soft parts re- 

 mains as high as in animals liberally supplied with these mineral 

 matters. In an experiment by these investigators it was found 

 that a cow, fed a ration deficient in lime, during a period of 3.5 

 months gave off 5.5 lbs. more lime in milk and excrements than was 



' Text Book of Physiology, p. P.32. 



- Research Bui. 5; Am. Jour. Phj^sioL, 1909. 



