HORMONES, VITAMINS, AUXIMONES 213 



Vitamin A. — This vitamin is found in dairy products, fats and 

 oils, egg yolk, carrots, leaf vegetables in general and spinach es- 

 pecially. Liver oils and dairy products are very rich in this vitamin, 

 which is fat soluble. Owing to the fact that it seems to be associated 

 with the carotinoids in leaves rich in chlorophyll, in carrots, 

 tomatoes, yellow corn, egg yolk, etc., it has been proposed that 

 it might be identical with one of the carotinoids. In plants or parts 

 of plants which contain no carotinoids, this vitamin has never been 

 found, and Mangelsdorf and Fraps (1931) found that the amount 

 of vitamin A in yellow corn varied with the number of genes for 

 yellowness present. Furthermore, white-seeded varieties with little 

 or none of this vitamin can form it when the gene for yellow color 

 is introduced by pollinating with a yellow-grained variety. If 

 vitamin A is not carotin, it is suggested by Capper that it may be 

 formed from carotin in the animal body, since rats suffering from 

 A-avitaminosis recovered when given carotin. Hence, although it 

 has not been definitely proved that vitamin A is a carotinoid, 

 their simultaneous occurrence in the same places must be of some 

 significance, and it is probable that carotin is a precursor of A, 

 i. e., its provitamin. 



The absence of vitamin A from the diet causes growth to stop 

 and produces an opacity of the cornea of the eye called xeroph- 

 thalmia, which may result in total blindness but is speedily re- 

 lieved by the addition of a little spinach and cream to the diet. 

 Its absence from the diet also causes a general weakening of the 

 tissues and a degeneration of the mucous membranes, which renders 

 them especially susceptible to infections. Night blindness (hemera- 

 lopia) seems also to be caused by the absence of this vitamin from 

 the diet. 



Vitamin B— This vitamin is water soluble and is found in fresh 

 vegetables, nuts, fruits, and yeast. The grains of the cereals con- 

 tain it in abundance, especially in the outer coat. It is not found 

 in sugars, starches, or fats, with the result that diets rich in these 

 foods will be short in vitamin B. Its absence in the diet of animals 

 causes polyneuritis and, in man, the diseases beriberi and neuritis. 

 For this reason, vitamin B is commonly called the " antineuritic 

 vitamin." Beriberi, which is associated with oedema and a weak- 

 ened heart, is found among rice-eating peoples if the rice has been 

 polished, in which case the pericarp containing the vitamin is 

 removed. If the entire grain is eaten, immunity from the disease 



