364 CARNEGIE INSTITUTION OF WASHINGTON. 



NUTRITION. 



Osborne, T. B., and L. B. Mendel, New Haven, Connecticut. Continuation 

 and extension ofivork on vegetable proteins. (For previous reports see Year 

 Books Nos. 3-12.) 



In the report for last year an account was given of the nutritive 

 properties of zein, the predominant protein of maize. The studies 

 there reported have been extended and the earHer results confirmed 

 and amplified. This defective protein has proved to be peculiarly 

 suitable as a basis for the solution of certain problems respecting 

 the role of amino-acids in maintenance and growth. Attention has 

 been directed this year to a study of the amounts of tryptophane and 

 lysine required for maintenance and growth. Tryptophane is unques- 

 tionably essential for certain as yet indefinable functions associated 

 with nutrition in maintenance alone. One per cent or less of trypto- 

 phane, calculated on the protein fed, is sufficient for the physiological 

 needs of maintenance. Similarly, experiments have been conducted 

 to learn the quantities of lysine that must be added to a lysine-free 

 diet before growth is manifested. The animal organism can appar- 

 ently supply whatever lysine may be needed in the wear-and-tear, or 

 maintenance functions, aside from construction of new tissues, from 

 its body reserves, more readily than it can furnish tryptophane. In 

 illustration an experiment may be cited in which a small rat was 

 maintained, without change in body-weight, over a period of six months 

 on a diet containing as its source of nitrogen only zein and tryptophane. 

 Prolonged maintenance has never been observed when the food yields 

 no tryptophane. Apparently far less lysine than tryptophane is needed 

 where tissue building is excluded. 



Aside from a purely theoretical interest there is an important prac- 

 tical aspect to this problem. It has already been pointed out that the 

 amino-acid deficiencies of our zein foods can be made good by sup- 

 plementing them with suitable proteins, provided these supply enough of 

 the essential amino-acids. Edestin and casein — low in their yield of 

 lysine and tryptophane respectively — can be made far more effective in 

 supplementing zein by adding an extra supply of lysine to the edestin or 

 tryptophane to the casein. The protein economy of nutrition evidently 

 depends largely on securing such a mixture of different proteins of un- 

 like amino-acid make-up as will give a total yield in which these nutrient 

 units are present in ideal proportional relationship to each other. 



The expectation that the application of these quantitative features of 

 nutrition to the practice of feeding our domestic animals will be of dis- 

 tinct advantage has already in part been realized by investigations 

 now under way on a large scale in some of the agricultural experiment 

 stations. In this connection we have now found that corn gluten, to 

 which some reference was made in our last report, can be successfully 

 supplemented by small additions of commercial "milk albumin." We 



