VITAMIN D 319 



reported as lacking vitamin D when in reality they contain a small, but 

 scientifically significant, amount of it. It is partly for this reason that 

 even some of the leading investigators of vitamin D do not yet realize 

 that it is widely distributed in nature and that foods not usually looked 

 upon as important sources (even foods upon which rickets sometimes 

 develops) may nevertheless contain significant amounts of vitamin D. 



Hess and his collaborators determine the vitamin D content of sub- 

 stances sometimes by using them to cure and sometimes to prevent 

 rickets in rats, as judged by X-ray and histological examinations of the 

 bones. They prefer experiments of the protective nature to those of 

 curative nature because, as they say, "in our experience there are 

 numerous complicating factors, difficult of interpretation, which may 

 bring about a greater or less degree of heaHng in bone." 



Bodily Storage of Vitamin D. — Drastically rickets-producing diets 

 may be so severe that rickets is produced in a short time regardless of 

 the stock diet from which the animals are taken. However, Hess, Wein- 

 stock and Tolstoi (1923) have reported instances in which animals were 

 "refractory"' to rickets due to the richness of the mothers' diet in 

 vitamin D and to the small sizes of litters born and reared. Young were 

 rendered susceptible to rickets by feeding the mother and young a less 

 adequate dietary throughout the suckling period. Resistance to rickets in 

 the young was also broken down by means of inadequate lactation 

 during this period as by forcing the mother to suckle young in addition 

 to her own litter. This deprivation of a liberal milk supply resulted in 

 an inability on the part of the young to store a reserve of the anti- 

 rachitic factor. They said: "Experiences of this kind indicate the neces- 

 sity of controlling the diet of experimental animals for the entire period 

 preceding the test. They also suggest that the diet of infants during the 

 first weeks of life may be of equal importance to the later development 

 of rickets." 



Further research in several laboratories has shown that the diet or 

 irradiation of the mother may have marked efifect upon the susceptibility 

 of her offspring to rickets doubtless largely if not mainly through 

 influencing the store of antirachitic vitamin in the body of the human 

 infant or other young animal. Goldblatt stated (1923), "When rats are 

 used which have only a small 'store' of fat-soluble organic factor (rats 

 bred from parents on an ordinary normal diet) grading the content of 

 that factor in their diet results in a corresponding gradation in the 

 percentage of calcium in their bones. Histologically, some of the rats on 

 the diets very deficient in fat-soluble organic factor show slight to severe 

 osteomalacia or rickets. When rats are used which have a large store of 



