674 ARTHUR ISAAC KENDALL 



incitants of. disease as diphtheria, anthrax, or typhoid bacilli (Vaughan). 

 The effects of carbohydrates and proteins upon the composition of the 

 cytoplasm of bacteria is discussed in the following section. 



6. Quantitative Measures of Bacterial Metabolism, the 



Effects of Utilizable Carbohydrates upon General 



Metabolism, and the Elementary Composition 



of the Bacterial Cell. 



' It is very evident that there are far-reaching theoretical and practical 

 applications of the theory that the "specificity of action of the vast 

 majority of bacteria depends upon their utilization of protein or protein 

 derivatives for energy." The application of the theory to the domain of 

 medicine is closely associated with the corollary thereof, namely, that the 

 "great majority of pathogenic bacteria become potentially lactic acid 

 bacteria when they are growing in an environment containing carbo- 

 hydrates or other non-nitrogenous compounds from which they can obtain 

 their energy." 



So sweeping an assertion would appear to require more than qualitative 

 evidence for its consideration or acceptance. Fortunately, such evidence 

 is available from several sources. 



The chemical basis for the proof of the theory of the sparing action of 

 utilizable carbohydrate awaited the development of methods for the study 

 of metabolism which were applicable to bacterial cultures. Qualitative 

 evidence has long been known, even though it was not appreciated for its 

 full significance. 



The very exact micro methods of urine analysis, developed and per- 

 fected by Folin and his associates (Folin(d)), have been found applicable 

 to the study of nitrogenous metabolism in cultures of bacteria (Kendall 

 and Farmer). The analytical data obtained are as precise as any obtain- 

 able for corresponding metabolic studies upon man or animals. Indeed, 

 in some respects they are of greater precision, inasmuch as the total nitro- 

 genous changes induced by various bacteria under varying cultural con- 

 ditions are always reproducible, since there is neither gain nor loss of 

 nitrogen during the experiment. 



The quantitative studies of bacterial metabolism were carried out in 

 precisely the same manner as a corresponding metabolic study upon man 

 or upon an experimental animal. Broadly speaking, the significance of 

 the results is the same for bacteria in either case. The results of these 

 quantitative metabolic studies appear to be very clear cut and definite; 

 they bear out exactly what has been indicated by qualitative observations, 

 namely, that utilizable carbohydrate added to protein culture media does 



