14 



Scientific Proceedings (55). 



Lewis's soluble red color is due to the indol substance. I have not 

 met with any insoluble red pigment in my tests with the Ehrlich 

 method. The purple or blue coloration appears to be independent 

 of indol production, as indicated by the following observations: 



1. If the tubes are shaken up with chloroform without the 

 addition of persulphate the supernatant liquid is colorless, but on 

 standing gradually assumes a purplish and eventually either a 

 purple-blue or blue color. Often of two duplicate tubes one was 

 purple-blue, the other blue. 



2. The addition of a few drops of fuming nitric acid or hydrogen 

 peroxide (oxidizing agents) to the decanted supernatant liquid 

 produces instantly the same changes in color observed gradually 

 on long exposure. 



3. The blue color reaction was obtained in uninoculated con- 

 trols and in solutions of peptone in distilled water which have been 

 treated with the aldehyde and concentrated hydrochloric acid. 

 This shows that this coloration is independent of the indol reaction. 



Since the aldehyde and acid alone do not give this reaction it 

 is apparent that the coloration must be due either to the peptone 

 or to some of the substances present in the peptone mixtures. 



7 (824) 



The influence of butter-fat on growth. 



By Thomas B. Osborne and Lafayette B. Mendel. 



[From the Laboratory of the Connecticut Agricultural Experiment 

 Station and the Sheffield Laboratory of Physiological Chem- 

 istry in Yale University, New Haven, Connecticut.] 



When young rats are fed on mixtures of isolated food substances 

 and inorganic salts such as the "protein-free milk" foods earlier 

 described by the authors, 1 they cease sooner or later to grow and 



1 Osborne and Mendel, "Feeding Experiments with Isolated Food-Substances," 

 Carnegie Institution of Washington, Publication 156, Parts I and II, 1911; "The 

 Role of Different Proteins in Nutrition and Growth," Science, XXXIV, pp. 722-732, 

 191 1 ; "Feeding Experiments with Fat-Free Food Mixtures," Journ. of Biol. Chem., 

 XII, pp. 81-89, 1912; " Beobachtungen iiber Wachstum bei Fiitterungsversuchen 

 mit isolierten Nahrungssubstanzen," Zeilschr.f. physiol. Chem., LXXX, pp. 307-370, 

 1912. 



