50 MILK AND ITS PROHUCTS AS FOODS 



made up of purified milk lonstitucnts. AIcC'(jllum and Da\'is 

 next tried the wheat seed or kernel. I'hey reasonef] that it con- 

 tained protein, carljohydrates anfl mineral salts and fats or oil, 

 and that if these were mostly equal in quality to those of milk 

 the only foodstuff that might have to be added would be a growth- 

 promoting fat. They first fed wheat alone anrl then tried the 

 improvement of it with resjiect to one dietar)- fartor at a time. 

 The following indicates the different combinations in which 

 wheat was fed, with results secured: 



(i) Wheal alone No growth, sliort hfe. 



(2) Wheat, [ilu> purified protein No .growth, short life. 



(3) Wheat plus a salt mi.xture whieh ga\'e it a 



mineral content, sin'.ilar to that ol milk Wt>" little growth 



(4) Wheal plus a growth-promoting fat (milk- 



fall No growth. 



(s) Wheat, plus the protein, jilus the salt mi.x- 

 ture (iooil growth lor a time, few or no 



\'oung, short life. 



(6) Wheat, jjlus protein, plus a growth-pro- 



moting fat (milk-fat). No growth, short life. 



(7) Wheat, plus the salt mixture, plus the 



growth-f)rom(jting fat (milk-fat) Fair growth for a time, few or no 



>'oung, short life. 



(5) ^\heat, plus protein, plus the salt mi.xture, 



plus a growth-pnjmoting fat (milk-fal ) Good growth, normal number of 



}'oung, good success in naring 



N'oung; life a[)proxiniately the 

 normal span. 



This series of experiments again pro\es the necessity of a 

 growth-promoting fat. But it does more than this; it shows that 

 the proteins and mineral matter from different sources are not 

 of equal value, those of milk Ijeing altogether superior in this 

 respect to those of such a food as wheat. Other experiments 

 pro\'ed that the seeds of other cereals are, like wheat, quite 

 incomplete in themselves as diets. 



In following up this in\'estigation it \\';is found that when 

 polished rice was substituted for wheat, in No. cS of the series of 

 experiments just outlined, the diet failed utterly to induce 

 growth. This was puzzling. The investigators had been able 

 to induce successful growth through feeding a diet composed of 



