VITAMIN A 287 



illustrated in the fact that these monkeys tended to die of the intestinal 

 diseases largely due to vitamin A deficiency, before the development of 

 ophthalmia. 



In this connection it may also be recalled that Wohlbach and Howe 

 did not observe ophthalmia in guinea pigs which showed the charac- 

 teristic histological changes resulting from vitamin A deficiency. Evi- 

 dently this deficiency may lead to a breakdown sometimes in one direc- 

 tion and sometimes in another. 



As the body is evidently able to store relatively large amounts of 

 vitamin A, and as this store is plainly a very important safeguard 

 and resource, it seems wise for those who can afford it to invest 

 rather liberally at all ages in food rich in vitamin A, knowing that in 

 this case the body will store the surplus to an extent and with an 

 efficiency which is not to be expected in the case of most other nutrients. 



Relation of Vitamin A to General Vigor. — As the result of his 

 extended investigation of the dietary properties of the various types 

 of food, McCollum concluded that dietaries deficient in vitamin A and 

 in calcium content are of relatively frequent occurrence; that such de- 

 ficiencies lower the vigor of the body and its ability to resist disease ; 

 and that as the result of such weakening there develops an increased 

 susceptibility, so that the incidence of any of a number of diseases (of 

 which tuberculosis serves as the outstanding example) may be largely 

 influenced by the adequacy of the diet as regards vitamin A. 



Experiments upon laboratory animals have quite definitely shown 

 that general vigor, as exhibited not only in growth but also in capacity 

 for reproduction and successful suckling of the young, is dependent 

 in large measure upon the amount of vitamin A in the food. Drum- 

 mond (1919b) stated that a liberal allowance of vitamin A resulted 

 in better reproduction, and McCollum as well as Steenbock and their 

 associates have repeatedly published implied confirmation of this finding 

 by reporting cases in which on diets which were being tested for vita- 

 min A the amount of this factor appeared adequate for growth but 

 not for reproduction, or for reproduction but not for rearing of the 

 young. Reynolds and Macomber (1921) have also found a decrease 

 in fertility to result from a paucity of vitamin A in the diet. More 

 recently, direct comparisons of dietaries otherwise identical but differ- 

 ing in their content of butter fat (or by the substitution of lard or hard- 

 ened vegetable oil for butter fat) have shown that such differences in 

 the vitamin A contents of two diets, even though both are adequate 

 for growth and apparently for general health, at least for a relatively 

 long time, may have a most marked influence upon the capacity to 



