44 McCOLLUM— RELATION OF DIET TO PELLAGRA. 



used in sufficient amounts the faults of the remainder of the food 

 mixture irrespective of the extent to which it is derived from either 

 seed, tuber, or root products. We have been able to plan satisfac- 

 tory diets of naturally occurring foods only by the inclusion of one 

 or more of these protective foods. The other group of natural 

 foodstuffs includes all seeds and seed products, such as the cereal 

 grains and their milling products (wheat flour, corn-meal, polished 

 rice, etc.), the legume seeds, tubers, edible roots, nuts, fruits, and 

 such cuts of meats as come from muscle tissue. 



In all cases where we have attempted to correct the dietary defi- 

 ciencies of a seed mixture by the addition of leaf only we have not 

 secured results so good as with milk, especially with such amounts 

 of leaf as would be acceptable in the human diet. The leafy foods 

 are eaten by Europeans and Americans only in a very water rich 

 condition, and it is difficult to secure the consumption of enough to 

 correct the deficiencies in the remainder of the diet. With animals, 

 when we have fed dry powdered mixtures containing as much as 

 25 to 40 per cent, of the diet derived from leaf and the remainder 

 from plant products of the storage organ class, the nutrition has 

 been very good in some instances, but not all combinations will be 

 equally valuable. Eggs are decidedly poorer in calcium than are 

 the leaves or milk, when only the part exclusive of the shell is con- 

 sidered. The shell serves as a source of lime to the developing 

 chick. Eggs do not, therefore, supplement food mixtures derived 

 from storage tissues with respect to calcium to the degree that milk 

 and leafy vegetables do. 



Even in such types of diet as contain one or more of the pro- 

 tective foods in fairly liberal amounts, it is certain that for such 

 rapidly growing species of animals as the hog and rat the inorganic 

 content is not entirely satisfactory, although it may be good enough 

 to enable the animal to perform all the functions of growth and 

 reproduction in a way which, in the absence of definite knowledge 

 of what the species is capable of, we should regard as normal. \\'e 

 have been accustomed to regard as normal an achievement in vigor 

 and well being both in man and animals which falls far short of that 

 seen in exceptional cases. The most important inorganic deficiency 

 in seed, tuber, and meat mixtures is calcium, and this is so pro- 



