^^^''J FOODS HUMAN NUTRITION. 61 



the natural foodstuffs. The latter may be of either inorganic or organic na- 

 ture. Aluminum and colloidal silica in the one class have been suggested and 

 gossypol of the cottonseed, and the toxic effect of the oil of the wheat kernel 

 which . . . [were] recently described may be cited as examples of the second." 



Methods of experimentation, which enable the isolation of individual dietary 

 factors and the evaluation of the individual dietary components in any natural 

 foodstuff, have been described in the present and former papers. They have 

 shown how the degree in which the shortcomings of one natural foodstuff are 

 corrected by the supplementary character of another can be studied by biological 

 methods sufficiently sensitive to yield results of great practical value. 



The authors state that the " practically complete success in the nutrition of 

 rats with strictly vegetarian diets made up of but three natural foodstuffs, and 

 the failure attending the employment of a wider variety in the food mixture, 

 emphasizes the fallacy of the assumption that the safest plan to insure perfect 

 nutrition is to include a wide variety in the selection of the constituents of the 

 diet. So long as definite knowledge is wanting concerning the specific nutri- 

 tive properties of the constituents of the diet, variety will unquestionably make 

 for safety, but will not by any means assure safety, and indeed can scarcely 

 secure the optimum result in any considerable percentage of cases." As soon 

 as an adequate knowledge of the specific properties of the natural foodstuffs and 

 their supplementary relations to each other is possessed, it will be possible to 

 compound fairly simple and monotonous diets which can be depended upon to 

 induce physiological well-being closely approximating the optimum. 



" The conscientious adherence to a vegetarian diet by one who has no ade- 

 quate technical knowledge regarding the subject of diet appears to be fraught 

 with danger, since among the food? of vegetable origin ordinarily consumed by 

 human beings several dietary factors are as a rule of an unsatisfactory 

 chemical character. It is certain that all of the components of a successful diet 

 are present in foods of plant origin." 



The distribution in plants of the fat-soluble A, the dietary essential of 

 butter fat, E. V. McCollum, N. Simmonds, and W. Pitz (Amer. Jour. Physiol., 

 41 (1916), No. 3, pp. 361-375, pi. 1, figs. 11).— To determine whether the indis- 

 pensable dietary factor, fat-soluble A, is present in foods of vegetable origin 

 or is a specific product of the mammary gland and the ovary of birds, various 

 types of substances of plant origin were fed with rations made up so as to 

 be wlioUy adequate when one of the growth-promoting foods was included 

 but in adequate when such foods were omitted. Records are given of the 

 growth of laboratory animals (rats), which were fed upon rations in which 

 maize, cottonseed, linseed, olive, sunflower-seed, and soy-bean oils, respectively, 

 were the only source of the dietary factor contained in butter fat. The results 

 of these experiments showed that the fat-soluble A is not found in fats and 

 oils of plant origin. 



Rats consuming cotton-seed oil prepared by ether extraction suffered in- 

 toxication within a few weeks and showed rapid loss of weight, but the com- 

 mercial bleached oil, prepared by hot pressing, could be fed at the same plane 

 of intake with no signs of injury. This corroborates the observations of other 

 investigators that the toxic factor " gossypol " is soluble in ether and is 

 present in the fat prepared by the use of this solvent. By feeding rations 

 which made it possible to test for toxicity of low intensity, the authors found 

 that wheat oil, linseed oil, and hydrogenated cotton-seed oil showed definite 

 but not severe toxic effects on young rats. 



It was observed in the experiments here reported that "ether extraction of 

 plant tissue does not remove the substance essential for growth which is con- 

 tained in butter fat. The obvious working hypothesis must for the present 



