VITAMINS 



219 



vegetable oils, particularly wheat germ oil, arc the richest sources. Whole 

 grain cereals, eggs, and peanuts are other rather good sources of vitamin 

 E. Fruits and vegetables as a class are rather poor sources, as are most 

 meats, fish, poultry and other animal products, except butter. Harris, 

 Quaife, and Swanson estimate that the average daily intake of alpha- 

 tocopherol in the United States is about 14 mg. per capita, of which nearly 

 8 mg. are obtained from fats and oils in the diet. 



Prevalence of vitamin E deficiency 



Various breeding troubles in farm animals such as horses and sheep 

 have been thought to result from inadequate intake of vitamin E, but it 

 is now practically certain that this is not the cause. Vitamin E deficiency 

 most probably does not occur except when the vitamin is deliberately 

 excluded from the diet. 



Claims have been made that vitamin E deficiency occurs quite com- 

 monly in women during pregnancy and that miscarriages, sterility, and 

 similar reproductive disorders of human beings have been helped by 

 administration of extra vitamin E. Other reports, however, contradict 

 these claims, so that at present the matter is still unsettled. 



VITAMIN K 



Physiological function 



When chicks or other fowls are fed a ration deficient in vitamin K, 

 eventually the blood ceases to clot within normal time with the result 

 that there is a marked tendency for hemorrhages to occur. This condi- 

 tion is characterized by bleeding from the pinfeathers and hemorrhages 

 into the subcutaneous tissues and muscles. The concentration of pro- 

 thrombin, one of the factors involved in clotting of blood, invariably is 

 found to be reduced in this deficiency disease. Just how vitamin K 

 influences the formation of prothrombin remains to be determined. Since 

 the sequence of changes involved in clotting of blood very likely is the 

 same for all species, it will not be surprising if further investigations 

 reveal a universal need of vitamin K. Experiments have demonstrated 

 that man, rabbits, mice, and perhaps cattle require this vitamin, although 

 deficiencies do not normally occur because adequate amounts usually 

 are provided by the food intake, or are synthesized by intestinal bacteria. 



Chemical nature 



Several substances exhibiting vitamin K activity have been found in 

 nature, and many more have been synthesized in the chemical laboratory. 



