326 CARNEGIE INSTITUTION OF WASHINGTON. 



olin prepared by extraction with sodium hydroxide is capable of induc- 

 ing some growth in rats. Boihng this preparation of phaseoUn fails 

 to increase its nutritive value. Determinations of the utilization of 

 these different preparations showed that only about 55 per cent of the 

 raw phaseolin, prepared by extraction with sodium chloride, is utilized, 

 whereas about 82 per cent of it is utihzed after it is boiled. The phase- 

 olin prepared by extraction with sodium hydroxide is utilized to the 

 extent of about 82 per cent when raw and 85 per cent when boiled. 

 These experiments are now being verified and extended in the hope 

 of gaining more precise knowledge as to the nutritive value of this 

 important leguminous seed and the explanation of the unexpected 

 phenomena noted. In this connection the recent observations of Falk 

 {Journal of Biological Chemistry, 1917, vol. 31, 97) on the effect of heat 

 and alkali on enzymes, proteins, and peptides in respect to their hydro- 

 lytic action on esters are suggestive that similar transformations in the 

 phaseolin molecule may be involved here. Falk points out that the 

 conditions which affect this hydrolytic action are the same as those 

 affecting tautomeric changes in the R-CO-NH-R grouping of known 

 organic compounds; and since the amino-acids are thus united in the 

 protein molecule it is not improbable that tautomeric changes of the 

 keto-lactam and enol-lactim type may occur under the influence of 

 heat or alkah, two conditions which we have found to affect the utiliza- 

 tion as well as nutritive value of phaseolin. 



Our report for last year stated that the use of yeast as a source 

 of food hormones would enable us greatly to extend the field of our 

 investigations. During the past year we have devoted a large part of 

 our time to studying the effect of small additions of this substance 

 to diets containing the inorganic constituents in the form of mixtures 

 of purified chemicals. We have directed especial attention to the 

 quantitative requirements of rats for such essential dietary factors sup- 

 plied by yeast, so that foods might be used which contained the least 

 possible additions of substances of unknown nature. 



We have found that there is a marked quantitative need for such 

 substances, but that individual animals differ to some extent in this 

 respect. Although the great majority of our rats grew normally when 

 1.5 per cent of dried yeast was added to the diet, some required as 

 much as 2 per cent, while others throve on as little as 1 per cent. A 

 very few needed only 0.5 per cent to make a corresponding growth. 



Having learned the proper quantity of yeast to use, we have under- 

 taken an elaborate series of experiments on the role of the individual 

 inorganic ions in the nutritive processes. To rations consisting of 

 highly purified proteins, starch, lactose, and fats, we have added 

 mixtures of inorganic elements in which the qualitative and quan- 

 titative relationship of the vai'ious ions was altered at will. The only 

 inorganic impurities which impaired the precision of these tests were 



