NOVEMBEE 24, 1911] 



SCIENCE 



731 



tions of diet is shown in a few charts in which 

 the curve of growth on mixed food is simul- 

 taneously plotted. 



How entirely different the results are when 

 an " inadequate " protein is alone furnished, 

 despite an abundant ingestion of food, is 

 strikingly shown by the drawings. The ani- 

 mals A and B were of one age and differed 

 simply in having been sustained on different 

 proteins. 



This drawing shows the influence of different 

 proteins on growth. A and B are rats of the same 

 brood which were fed from the time of weaning 

 on foods of the same composition except that the 

 diet given to A contained pure casein while that 

 given to B contained pure gliadin as its only pro- 

 tein. The appearance of B at the age of 140 days 

 closely resembles that of C, a normally nourished 

 rat, which at the age of 36 days had the same 

 weight as B. (Sketch from photographs in Publi- 

 cation 156, Part II., Carnegie Institution of Wash- 

 ingt.on, 1911.) 



It will be noted that the older but stunted 

 animals do not vary materially in size from 

 properly nourished younger animals which 

 have attained the same body weight. Herein 

 they differ essentially from young animals 

 which, maintained at constant body weight by 

 underfeeding, continue to grow in size. Such 

 conditions have been described in cattle," 



"Waters, Proceedings Society for the Promo- 

 tion of Agricultural Science, 1908, XXIX., p. 3; 

 also Ibid., XXX., p. 71. 



=°Aron, Biochemische Zeitschrift, 1910, XXX.^ 

 p. 207; Philippine Journal of Science, Sec. B., 

 1911, VI., p. 1. 



dogs '° and children ;^ and they lead to dispro- 

 portioned forms. Our (malnourished rather 

 than undernourished) rats have merely main- 

 tained themselves, if we except the possibility 

 of a continued development of the nervous 

 system of which we have furnished some evi- 

 dence elsewhere.^^ 



Aside from the nutritive inequalities of dif- 

 ferent proteins, as well as the apparent com- 

 parable suitability of chemically and biolog- 

 ically unlike proteins — all of which remains to 

 be subjected to more refined experimental in- 

 vestigation — it is worth while to point out 

 numerous other incidental findings. Animals 

 which have grown from small size, e. g., 40 

 grams, to adult form, e. g., 160 grams, and 

 have thus quadrupled their weight on a diet 

 furnishing its nitrogen in the form of a simple 

 protein like edestin, have by some process per- 

 fected the synthesis of purines and nucleo- 

 proteins, perchance of phosphoproteins and 

 nitrogenous phosphatides, and of ferruginous 

 proteins (like hemoglobin) from iron-free pro- 

 tein precursors and " inorganic iron." 



With what powers of synthesis in such 

 directions is the body provided by nature? 

 What modifications, if any, can be introduced 

 into the organism in respect to structure, 

 function or inheritance by the possibility of a 

 successfully regulated control of the character 

 of the most important foodstuff, the protein? 

 Such physiological and broader biological 

 questions appear to lend themselves to experi- 

 mental study by the methods which we have 

 initiated. There are, further, pathological 

 aspects involving abnormal growth, dwarfism, 

 recuperation and senescence which similarly 

 suggest themselves. The program for the 

 future is limited only by the success and efii- 

 ciency of the methods adopted. 



To the biological chemist, no feature of 

 these problems appeals more strongly, perhaps, 

 than the question of how an organism can 

 build such diverse nitrogenous tissues from a 



'' Fleisohner, Archives of Pediatrics, October, 

 1906. 



^= Osborne and Mendel, Carnegie Institution of 

 Washington, Publication 156, Part II. 



