Effect of Acids on Typhoid and Colon Bacilli 267 



muscle of the frog, terrapin, and guinea-pig was reduced from one 

 half to three-fourths in the presence of white of egg, partially dialyzed 

 serum, peptone, or starch. In some cases a combination between the 

 inorganic body and the proteid has been demonstrated by freezing- 

 point determinations, but in other cases particularly with the neutral 

 salts, this has not been shown. As the authors suggest, these experi- 

 ments point to the existence of ^^physiological compounds which are 

 not demonstrable at all by chemical methods, but only by the 

 reactions of living tissues." 



2. OBJPXT AND METHODS OF THE PRESENT INVESTIGATION. 



The present investigation was begun with the intention of deter- 

 mining the effect of acid wastes in sewage upon the viability of the 

 typhoid bacillus under practical conditions. It soon appeared, 

 however, that the problem was too complex to be attacked in any 

 general way without the preliminary determination of certain of the 

 individual factors involved, under definitely controlled conditions. 

 We have therefore attempted to find the disinfectant power of tw(~ 

 mineral acids and two organic acids upon the typhoid bacillus in tap 

 water and in the presence of peptone, and have controlled these 

 experiments by a parallel series wdth the colon bacillus. The results, 

 besides their specific value as determinations of the reactions of these 

 two organisms to dilute acids, have a certain interest in relation to 

 the general theory of disinfection. In all the experiments reviewed 

 above, except Dial's, the acids used were tested in only a few widely 

 differing strengths, so that the parallelism between disinfectant action 

 and dissociation was not established with any great exactness. In 

 the work of Kronig and Paul on anthrax spores and the various studies 

 on the mold fungi, it was necessary to use such strong solutions 

 that ionic effects were largely masked by the influence of the undis- 

 sociated molecule, and in the studies of Kahlenberg and True and 

 Heald on the phanerogams it was evident that with such complex 

 organisms many other factors than the direct effect on protoi)lasm 

 come into play. There was room, therefore, for a series of experi- 

 ments on organisms sensitive to very dilute acids, carried out in 

 suffK-ient detail to show definitely the relations between toxicity 

 and dissociation. 



