126 



GENERAL ZOOLOGY 



fresh vegetables and fruits, the outer coating of grains, 

 many fats, yeast, liver, milk, and eggs. 



So far the vitamins have usually been named as vitamins 

 A, B, C, D, and E. It is probable that others beyond these 

 five may be discovered. Vitamin A is a growth-promoting 

 vitamin. Animals fed on a diet lacking nothing but this 

 vitamin fail to grow normally and develop diseased eyes 



Fig. 69. These guinea pigs were from the same litter 



The smaller one shows the effects of a diet deficient in vitamins. (Courtesy of 

 Dr. Percy R. Howe, Forsyth Dental Infirmary) 



and bones and have a decidedly unnourished appearance. 

 This vitamin is found most abundantly in milk, eggs, but- 

 ter, and cod-liver oil. 



Vitamin B is also growth-promoting. It occurs in seeds, 

 in yeast and egg yolks, and to a smaller extent in meat, milk, 

 and certain vegetables and fruits. Its complete lack in the 

 diet produces inflammation of the nerves, which may result 

 in paralysis and death. 



Vitamin C occurs abundantly in citrus fruits, tomatoes, 

 and some other fresh fruits and vegetables. Milk, lean meat, 

 and some dried vegetables contain vitamin C in smaller 

 amounts. Lack of this vitamin produces the skin disease 

 called scurvy. 



Vitamin D is especially abundant in cod-liver oil. Lack 

 of this vitamin leads to poor bone formation and a disease 

 called rickets. 



