732 



SCIENCE 



[N. S. Vol. XXXrv. No. 882 



single dietary protein. It is true that the 

 newer conceptions of the extensive role of 

 hydrolysis in digestion prior to absorption 

 have extended the inquiry a step further, so 

 that we may ask what is the minimum of this 

 or that amino-acid or simple polypeptide re- 

 quired. But we have seen rats grow for 

 months with casein — ^thoroughly purified and 

 glycocoll-free — as the sole source of these 

 amino-acids. During this time, one animal 

 even brought forth two broods of young and 

 secreted milk in sufiicient quantity to bring 

 her young to the age when they were able to 

 care for themselves. Another pair of rats 

 maintained 178 days on gliadin as the sole 

 protein of the diet produced healthy young and 

 successfully reared them. It is most unlikely 

 from all that is otherwise known, that the 

 tissues of our experimental animals are chem- 

 ically imperfect or essentially unlike those of 

 normally fed rats which presumably do contain 

 glycocoll and lysine groups. Have we hereto- 

 fore underrated the ultimate synthetic capac- 

 ities of animal cells ? "^ 



The observation that animals long main- 

 tained on diets of the character used in our 

 feeding trials voraciously eat the feces of 

 normally fed rats led us to experiment in 

 another direction. It has been noted as a 

 result of this that in a not inconsiderable 

 number of instances the feeding of small por- 

 tions of " normal " rat feces tended to check 

 the decline of rats kept on pastes of isolated 

 food substances containing the earlier salt 

 mixture. The possibility of altering the 

 bacterial flora of the alimentary tract by 

 dietetic conditions at once suggests itself 

 in this connection, and reference may be made 

 to the significant studies of Herter and Ken- 

 dall,"* among others, which elucidate this ques- 



^ One is reminded of the recent studies of 

 Kjioop, Zeitschrift fiir physiologische Chemie, 

 1910, LXVII., p. 489, and Embden and Schmitz, 

 Biochemische Zeitschrift, 1910, XXIX, p. 423, 

 bearing on such possibilities. Cf. Mendel, Ergeb- 

 nisse der Fhysiologie, 1912, XI. 



-* Herter, ' ' The Common Bacterial Infections of 

 the Digestive Tract, ' ' The Macmillan Co. ; Herter 

 and Kendall, Journal of Biological Chemistry, 



tion. To what extent is the cooperation of 

 bacteria either essential or useful in the ali- 

 mentary functions? This is, indeed, still a 

 debated question.'^ But one can not dispel the 

 idea that bacteria might, after all, enter into 

 reconstructive reactions which may furnish 

 new nitrogenous complexes from amino-acids. 

 Viewed in this light, the immediate hydrolysis 

 products of our foodstuils may become avail- 

 able only after they have in greater or less 

 part been reconstructed by the preeminently 

 synthetic symbiotic bacteria into products of 

 more uniform character, possibly widely dif- 

 ferent from the original intake. Nucleopro- 

 tein synthesis, for example, may thus become 

 referable to bacterial intervention; and the 

 subtle influence of the indeterminable non- 

 protein factors may lie in some measure in the 

 regulation which they exert upon the micro- 

 organisms of the gastro-intestinal tract.^" In 

 any event such suggestions need to be dealt 

 with. 



It is hoped to continue these nutrition 

 studies, the possible scope of which has barely 

 been indicated in what has gone before. They 

 seem to us to justify the effort which has been 

 involved. Indeed only by unremitting re- 

 gard for details, such as the careful purifica- 

 tion and preparation of the materials fed and 

 attention to the animals, can the uncertain 

 factors be limited, comparable results obtained 

 and definite conclusions safely drawn. We 

 realize that only a beginning has been made, 

 and believe that further progress is possible. 



Thomas B. Osborne, 

 Connecticut Agricultural 

 Experiment Station 



Lafayette B. Mendel, 

 Sheffield Laboratory of 

 Physiological Chemistry, 

 Tale University 

 New Haven, Connecticut 



1910, VII., p. 203; Kendall, Journal of the Amer- 

 ican Medical Association, April 15, 1911. 



^ NuttaU and Thierfelder, Zeitschrift fiir physi- 

 ologische Chemie, 1895, XXI., p. 109; Schottelius, 

 Archiv fur Hygiene, 1908, 67, pp. 177-208. 



^ Cf . Armsby, ' ' The Nutritive Value of the 

 Non-protein of Feeding Stuffs," Bureau of Ani- 

 mal Industry, Bulletin 139, 1911. 



