THE REACTION TO FOOD 343 



Mississippi Valley the incidence of the disease has been 

 considerably less, but it rose again on that occasion. 



A common defect in the diet of Americans and Europeans 

 is that of a deficiency of calcium together with an excess of 

 phosphorus in the food supply. It has been clearly demon- 

 strated that an unfavorable ratio between these two elements 

 in the food tends to disturb the metabohc processes in the 

 bones. The disease known as rickets can readily be produced 

 in animals in either of two ways: by feeding a diet low in 

 calcium and disproportionately rich in phosphorus, or 

 deficient in phorphorus and disproportionately rich in 

 calcium. In either case in order to have the disease develop 

 there must be a paucity of sunHght containing radiations 

 of ultraviolet wave length, and also of vitamin d. Marked 

 deficiency of protein in the diet over a considerable period, 

 as when the population is at war or approaching famine 

 conditions and is forced to subsist upon a diet of cabbage, 

 lettuce and other green foods has been observed to cause 

 epidemic dropsy. 



The idea prevails in many minds that so long as people 

 escape developing the characteristic syndromes of the 

 deficiency diseases, the diet may be said to be adequate. This 

 rests upon a failure to appreciate nice distinctions in physio- 

 logical well-being. In experimental work with animals it has 

 been found readily possible to distinguish a number of grades 

 of malnutrition. Diets which are very badly constituted may 

 result in total failure of young creatures to grow, or the 

 diet may be sufficiently good so that growth may take 

 place but at two-thirds of the normal rate, the animals 

 eventually presenting the appearance of runts. Again the 

 diet may be good enough to induce growth at the normal 

 rate until adult size is attained and yet be inadequate 

 for the support of physiological well-being throughout the 

 normal span of life. 



We have often recorded the chronological age at which 

 distinct signs of seniHty appear in comparatively young 

 animals as evidence of the quahty of the diet. Again, crea- 

 tures have been observed to develop in a manner apparently 

 normal and in adult fife appear to be well-nourished, yet 

 fail in one or another way in fertihty: (a) having no young, 



