48 MILK AND ITS PRODUCTS AS FOODS 



These would be what McCollum terms the " fat-soluble A," 

 which is found in milk -fat but not to any appreciable extent in 

 the ordinary fats, and the " water-soluble B," which is more 

 generally distributed in foods, particularly in diets of mixed 

 foods. 



Bloch, a Danish physician, observed about forty cases of 

 severe eye trouble, accompanied by ulceration, in children near 

 Copenhagen. This would, without doubt, have ended in blind- 

 ness. These children had been receiving skim-milk, instead of 

 whole milk, in their diet, and were practically deprived of milk- 

 fat in their food. When the younger of them were given mother's 

 milk, and the older either cow's milk or cod liver oil, they 

 responded and recovered. He attributed the trouble to the lack 

 of fat in their foods ; but it will be noted that in all cases the real 

 cause of recovery was the feeding of fats containing the, as yet, 

 unidentified fat-soluble which is present in the fats of milk, the 

 yolk of egg, the liver and other body glands, and the leaves of 

 plants, particularly such plants as alfalfa and the clovers. 



Mori found fourteen hundred cases of similar eye trouble 

 amongst children in Japan; these responded to the feeding of 

 chicken livers. 



It has been found both by McCollum and Davis, and by 

 Osborne and Mendel that milk-fat contains a fat-like or fat- 

 soluble substance whose presence or absence in a food, otherwise 

 entirely satisfactory, means the difference between growth and 

 no growth in the young. In addition to this, both these pairs of 

 investigators found that, deprived of such a fat as milk-fat, the 

 young animal would develop a disease of the eyes which would 

 ultimately cause blindness and, if persisted in, would end in 

 death; but that if this fat were restored in time the eyes would 

 become normal again and the young animal would return to its 

 former health and vigor and resume normal growth. 



It would be unfair to credit any one man, or set of men 

 collaborating with each other, with the discoveries that have 

 been made during the past fifteen or twenty years and par- 

 ticularly within more recent years through the biological study 

 of foods. The list of investigators is rather a formidable one. 



