2 Journal of Agricultural Research voi. xii, no. i 



cordant results is probably due in the main to differences in the details of procediure 

 in the experimental work. 



Hart and Bentley/ of the Wisconsin Experiment Station, comment 

 unfavorably on the lack of agreement between the results obtained by 

 Grindley, Slater, et al., and those obtained by Nollau for the amount 

 of the different amino-acid groups contained in feeding stuffs. They 

 state that whether accurate determinations of any or all the amino acids 

 can be secured when the hydrolyzing proteins are in contact with hydro- 

 lyzing carbohydrates must first be determined before these data can be 

 accepted as final. 



Presumably in order to substantiate the theory in regard to the effect 

 of hydrolyzing carbohydrates on the different amino-acid groups in pro- 

 teins. Hart and Sure ^ have published results obtained upon the hy- 

 drolysis of casein, alone and in the presence of a number of different 

 carbohydrates. In one of their experiments, 2.4 gm. of casein and 12 

 gm. of starch were hydrolyzed by boiling in 20 per cent hydrochloric 

 acid for a period of 48 hours. The result obtained for lysin in this ex- 

 periment shows that approximately 50 per cent of this amino-acid 

 group has been changed to some other form of combination. They 

 summarize their results in part as follows : 



The Van Slyke method of protein analysis, applied to casein, hydrolyzed in the 

 presence of various carbohydrates, brings about a total redistribution of the amino- 

 acids varying with the nature of the carbohydrate employed. This work on casein 

 and Gortner's work on fibrin, hydrolyzed in the presence of cellulose, definitely show 

 the inapplicability of the method of direct hydrolysis for the estimation of amino- 

 acids in feeding stuSs by Van Slyke 's method. The results so secured will be inac- 

 curate. 



Upon the publication of Hart and Sure's results, it appeared to the 

 writer that their conclusions were much broader than their experiments 

 justified. In fact, Hart and Bentley^ make statements which appear to 

 be merely forecastings rather than conclusions arrived at by experi- 

 mentation. In order to be able to say positively that the Van Slyke 

 method for protein analysis can not be applied directly to heterogeneous 

 mixtures of protein and carbohydrate requires much further experi- 

 mentation. It is by no means to be taken for granted that results obtain- 

 ed on a 48-hour digestion will be the same as those carried on for a shorter 

 length of time. 



It therefore occurred to the writer that a duplication of the experiment 

 of Hart and Sure upon the effect produced on the hydrolysis of casein 

 by the presence of starch, in which the time of digestion varied, would 

 afford more conclusive evidence on this subject. Accordingly, five ex- 

 periments were planned, as follows: 



' Hart, E. B., and Bentley, W. H. the character OF the water-soluble nitrogen of some com- 

 mon FEEDING STUFFS. In Jour. Biol. Chem., v. 22, no. 3, p. 477-483. 1915. 



* and Sure, Barnett. The influence of carbohydrates on the accuracy of the van slyke 



method in the hydrolysis of casein. In Jour. Biol. Chem., v. 28, no. i, p. 241-249. 1916. 



3 Hart, E. B., and BentlEy, W. H. Op. cit. 



