GROWTH AND NUTRITION 77 



somewhat subnormal. Some of the animals that had stopped 

 growing at subnormal weights, again resumed growth when 

 given a mixed diet, thus indicating that this high protein diet 

 left something to be desired. 



In connection with diets of a high protein content the ques- 

 tion of damage to the kidney often arises. Newburgh 7 states that 

 a high protein dietary is associated with renal disorders. Pol- 

 vogt, McCollum, and Simmonds 8 state that the kidneys of rats 

 suffer lesions from excessive protein feeding. Osborne and 

 Mendel 9 report that though they fed protein at a higher level 

 than did the Johns Hopkins group, their animals exhibited no 

 lesions. The kidneys were, however, about one-third larger, 

 and about twice as heavy as the kidneys of normal control rats. 

 The view of Osborne and Mendel is supported by A. J. 

 Miller. 10 



The Inorganic Nutrients. It has been recognized for years 

 that certain mineral elements are indispensable components of 

 the dietary, but knowledge of their specific functions is in most 

 instances very limited. In general, therefore, it is our practice 

 to speak of the "ash" content of foods when we consider their 

 content of mineral matter, though it has become a custom to 

 give separate consideration to calcium and phosphorus. The 

 reason for that is, of course, obvious. Growing animals, and 

 those secreting milk, have requirements for those elements rep- 

 resenting quantities of fairly large magnitude, and the mini- 

 mum quantities required are fairly well defined at present. In 

 the case of the other elements, however, there is almost no good 

 evidence as to the minimum requirement for growth or as to any 

 specific role they play in that process. 



Some of the feeds commonly employed are notably deficient 

 in mineral elements and it was recognized in the early history 

 of the science of nutrition that the cereals, notably maize, are 

 deficient in both protein and mineral constituents. Some years 

 ago the writer was associated for a time with an investigation in 

 which swine were used for a study of the nutritional properties 



