48 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



and also in Europe discovered that if animals were fed upon 

 feed from which all fatty substances had been removed, 

 they failed to thrive. Many became blind and finally they 

 died. If such fats as lard, olive oil, or cotton seed oil were 

 added to the ration, no improvement resulted. If butter fat, 

 whole milk, cream or the fat from egg yolks were added, 

 the diet was made complete and the animals made normal 

 growth. 



What was lacking in the ration was, therefore, not fat, 

 but some substance which was soluble in fat and was hence 

 carried along in the butter fat and egg fat. This was vit- 

 amin A. What had cured the animals was not protein, car- 

 bohydrates, fats or mineral compounds in the milk added 

 to the ration, but the. very minute amount of this remark- 

 able vitamin. 



Even yet, the most painstaking and clevel* efforts of 

 skilled chemists have failed to discover just what this mar- 

 velous substance is in butter fat and in egg fat. The amount 

 is so small and perchance the substance is so complex that 

 it may never be possible to isolate and identify it. So for 

 the present, and perhaps for all time we can know this 

 vitamin merely through the results produced by its absence 

 or its presence in food. 



Where animals are fed rations containing too little of 

 the vitamin, a peculiar eye disease may develop which 

 eventually causes blindness. Furthermore, at least some 

 animals are especially susceptible to pneumonia or other 

 respiratory diseases when the supply of the vitamin is in- 

 sufficient. 



If young animals are fed rations containing none of 

 this vitamin, they invariably fail to grow. Also no young 

 are ever produced and reared by females fed rations low 

 in this substance. It is, therefore, absolutely essential for 

 the life of all higher animals, and is needed by mature ani- 

 mals as well as those that are young and growing. 



It has been found that certain other foods besides milk 

 and eggs are rich in this vitamin. Most important from the 

 standpoint of stock feeding is the fact that all green-leaved 

 plants contain an abundance of it. Therefore, all stock 



