1919] FOODS — HUMAN NUTRITION. 559 



of fat-soluble A in the diet of the adult and the connection between the metab- 

 olism of fat-soluble A and the fat of the diet. 



The need of the organism for vitamins is apparently proportional to the de- 

 crease in vitality, after a certain point the organism being incapable of de- 

 veloping in a medium containing no vitamins. In full activity, however, the 

 organism seems to have the power of existing without vitamins or of synthe- 

 sizing them. 



The* lipoids as indispensable constituents of food, W. Stepp {Ztschr. Biol., 

 66 {1916), No. 9, pp. 365-3S6; abs. in Zcntbl. Biochem. u. Biophys., 19 {1918), 

 No. 14-15, p. 398).— The author's earlier experiments (E. S. R., 31, p. 861) have 

 been repeated, using white mice again as the experimental animal and dog 

 biscuit from which the lipoids had been extracted with alcohol and ether as 

 the basal diet. 



It was found that prepared dog biscuit alone, dog biscuit with lipoids, and 

 dog biscuit with a vitamin preparation (orypan) were inadequate for nutri- 

 tion, but that the combination of dog biscuit, pure lipoids, and vitamins pro- 

 duced satisfactory growth. In the opinion of the author this indicates the 

 indispensability of lipoids for nutrition. 



Researches on the fat-soluble accessory substance, I— II, J. C. Dkummond 

 {Biochem. Jour., 13 {1919), No. 1, pp. 81-102). — Two papers are presented: 



I. Observations iipon its nature and properties (pp. 81-94). — The stand- 

 ardized method adopted by the author in testing substances for the presence 

 of fat-soluble A is as follows: Young healthy rats selected from home bred 

 stock and weighing about 50 gm. each are fed upon an artilicial ration consist- 

 ing of purified casein 20 parts, purified starch 50, salt mixture 5, yeast extract 

 (source of water-soluble B) 5, butter fat (source of fat-soluble A) 15, and 

 filtered orange juice (source of water-soluble C) 5 parts. The rats which give 

 evidence of a normal power of growth are removed from the complete ration 

 when they have attained an average body weight of 70 to 80 gm., and are given 

 a similar dietary in which the butter fat has been replaced by an equivalent 

 amount of hardened linseed oil which is known to be deficient in fat-soluble A. 

 When it is definitely established that growth is inhibited by this deficiency of 

 fat-soluble A, the linseed oil is wholly or partially replaced by the substance to 

 l)e tested and the behavior of the animal closely watched for a period of from 

 4 to 6 weeks. Absence of fat-soluble A is indicated by failui-e to grow, followed 

 by a decline in health accompanied by the characteristic eye condition. 



The results obtained in a study of the properties of fat-soluble A according 

 to the above method are summarized as follows : 



Fat-soluble A, present in certain oils such as butter fat and whale oil, is 

 readily destroyed by exposure for one hour to a temperature of 100° C, by 

 exposure for a longer period of time to temperatures ranging from 50 to 100°, 

 and by exposure for several weeks to a temperature of 37°. The destruction is 

 apparently not a result of oxidation or hydrolysis. 



Fat-soluble A is not extracted from oils by water or dilute acid, but is 

 soluble in alcohol and may be removed in small quantity from oils by cold 

 extraction with alcohol. Hydrolysis of oils in a nonaqueous medium at room 

 temperature causes disappearance of fat-soluble A. 



In regard to its composition, fat-soluble A has not been identified with any 

 of the recognized components of fats such as glycerol, saturated or unsaturated 

 fatty acids, cholesterol, lecithin, phosphatids, or lipochromes. No evidence has 

 been obtained to suggest that it is not a single substance, but indications point 

 to its being a labile substance of ill-defined constitution. 



II. Observations on its role in nutrition a)i(l influence on fat metabolism 

 (pp. 95-102). — The studies reported in this paper concern the indispensability 



