REACTION OF CULTURE MEDIA. 845 



3. The "comma form," with yariation. only in regard to length and 

 thickness. 



4. The "coccus form," which varies in its diameter assuming some- 

 times an oval form and then again a spherical one. 



A most important factor in the campaign against an epidemic of cholera 

 is the discovery of every source and locality of infection. The finding and 

 disinfection of these sources is accomplished by the detection of the cholera 

 vibrio in stools, waters, sewage, and other places, and its morphology 

 may be a very important factor in its detection. In stained prepara- 

 tions from cultures in peptone, or even in those made directly from the 

 stools, the form of the vibrio is often the starting point in the detection 

 of the cholera organism. If we examine Table 2, we perceive that in 

 4.616 per cent of the different strains of the cholera vibrio this organism 

 assumed the coccus form, while in 12.307 per cent it appeared as a 

 rod. Therefore, if we should neglect the further examination by means 

 of plate cultures and the performance of the agglutinative and bac- 

 teriolytic reactions, we would fail in the detection of the cholera vibrio 

 in 16.923 per cent of the cases. Moreover, if we pursue the complete 

 bacteriological investigation only in those cultures in which the typical 

 vibrio form is present, we would fail in the detection of the cholera 

 organism in .57.691 per cent of the cholera cases. Therefore, in the 

 examination of suspected material for the cholera organism, much 

 assistance can frequently be given if the three solutions of peptone of 

 different reactions are employed, since in one of these it is very likely 

 that the organism will assume its typical vibrio form. 



It seems to me that most authors do not lay sufficient stress upon 

 the reaction of the peptone solution used in isolating the cholera vibrio. 

 It is usually merely stated that the peptone solution should he slightly 

 alkaline. In Prussia, 0.3 per cent of crystallized soda after neutraliza- 

 tion to litmus, is employed for the media, and most German authors 

 agree that this is the optimum reaction for the media; that is, 0.3 per 

 cent alkaline to litmus. Lehmann ■' thinks it is preferable to use 

 2 per cent normal sodium hydroxide, or 1 per cent crystallized or 

 0.3 per cent water free soda after neutralization with phenolphthalein. 

 However, with peptone solution of but one degi'ee of alkalinity as 

 stated above, it is not uncommon to fail to discover cholera vibrios from 

 the microscopical examination owing to the fact that they do not appear 

 in typical form. 



'Lehmann & Neumann: Bacteriologische Diagnostik. Munich, 4th ed. (1007) 

 487. 



