174 



THE INTERNAL ENVIRONMENT OF THE BODY 



Part III 



Fig. 11.3. Left, Dog with vitamin A deficiency causing xerophthalmia, a dry- 

 ness of the eyeballs. Right, Same dog after treatment with cod liver oil for 10 

 days. From early times it has been known that night-blindness and xerophthalmia 

 are associated with sparsity of fat in the diet. In man the most sensitive test for lack 

 of vitamin A is loss of adaptation to darkness. The visual purple in the retina of 

 the eye is a derivative of vitamin A. (After Steenbock, Nelson, and Hart. Courtesy, 

 Bogert: Nutrition and Physical Fitness, ed. 3. Philadelphia, W. B. Saunders Co., 

 1941.) 



Table 11.2 



Minerals and/or Trace Elements* Required by the Body of man and Other 



Mammals 



* Authorities differ as to whether some of these substances are in small enough amounts 

 to be classed as trace elements. 



