. Principles of veterinary science; a text-book for use in agricultural schools. Veterinary medicine. 108 PRINCIPLES OP VETERINARY SCIENCE tioned, other investigators had announced the discovery in foodstuffs of a substance or substances necessary for growth to which they gave the name vitamines. However, they had no conception of the nature of vitamines until McCollum published the results of his work showing that they contain two separate and distinct factors, each of which differs in several ways from the other and both of which are equally important, as is shown by the fact that the absenc
. Principles of veterinary science; a text-book for use in agricultural schools. Veterinary medicine. 108 PRINCIPLES OP VETERINARY SCIENCE tioned, other investigators had announced the discovery in foodstuffs of a substance or substances necessary for growth to which they gave the name vitamines. However, they had no conception of the nature of vitamines until McCollum published the results of his work showing that they contain two separate and distinct factors, each of which differs in several ways from the other and both of which are equally important, as is shown by the fact that the absence of either will cause failure of growth. He has termed one the fat soluble A and the other the water soluble B factor. Although nobody has yet determined their chemical properties, it is known that they are not destroyed by moderately high degrees of Fig. 32.—Pigs of the same age on a nutrition experiment. The animal on the left (55 pounds) received a ration of parts of wheat meal and parts of wheat gluten. The animal on the right (165 pounds) received a ration of wheat meal and skim-milk fed in approximately the proportions of 1:1. (Wisconsin Bulletin 291.) Later the presence of both the essential fat and water soluble substances was demonstrated in alfalfa, clover, and cabbage leaves. It is probable that the leaves of all forage plants con- tain them. Be this as it may, there is no doubt that all seeds contain a much smaller amount of these substances than do the leaves. Butterf at contains an abundance of the fat soluble A, and skim-milk an abundance of the water soluble B. However, neither class of vitamines is constructed by the cow. The animal concentrates them from the feed and places them in the milk. In other words, the cow's feed must contain them, otherwise she would be unable to secrete normal milk. One would expect to find the fat soluble A in all common fats. Digitized by Microsoft®. Please note that these images are extracted from scanned page
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