GROWTH 421 



lum 1 found that confined pigs on a ration of maize alone and 

 drinking distilled water failed to grow, while the addition of an 

 artificial mixture of salts enabled nearly normal growth to be 

 made. 



With cattle and sheep a deficiency of calcium is not usually 

 to be feared, since roughages are usually rich in this element. 

 Straw and roots, however, are rather low in calcium and so are 

 certain by-product feeds, especially those like gluten feed and 

 meal, distiller's grains, etc., which have been subject to ex- 

 traction with water. 



497. Forms of phosphorus. A much discussed question is 

 that of the relative value of organic and inorganic phosphorus 

 compounds. It was stated in Chapter V (258), that the animal 

 body is apparently able to synthesize its organic phosphorus 

 compounds from inorganic phosphorus. Forbes 2 has given 

 a very complete review of the literature of this subject. His 

 general conclusion is that it has not been proven that a supply 

 of organic phosphorus is essential, although he regards the 

 proof that inorganic phosphorus can serve all the purposes for 

 which any animal needs phosphorus as being incomplete. As 

 regards the relative efficiency of the two, the facts already noted 

 in Chapter IX (437, 438) and in the following paragraphs, re- 

 garding the importance of accessory substances, in particular 

 the so-called growth substances, in nutrition strongly suggest 

 that the apparent superiority of organic phosphorus which has 

 been observed in some experiments may have been due to the 

 presence of such substances accompanying the organic phos- 

 phorus compounds and not to the latter as such. 



Accessory substances 



498. Relation of fats to growth. It was mentioned in 

 Chapter V (265), in considering the functions of the nutrients, 

 that it had apparently been shown that the presence of a certain 

 minimum amount of fat (or at least of ether-soluble sub- 

 stances lipoids) was necessary for growth. Later investi- 

 gations, however, have led to a different interpretation of these 



1 Jour. Biol. Chem., 19 (1914), 373. 



2 Ohio Expt. Sta., Tech. Bui. 5, pp. 318 to 365. 



