io8 THE BACTERIA IN ASIATIC CHOLERA. [CH. 



distinctly acid, even after a few days only, and long before 

 the climax of growth is reached. I have in one instance 

 convinced myself that they are capable of growing (though 

 of course not copiously, any more than in the case of many 

 other bacteria), even when the nutritive medium (broth) was 

 at the outset just faintly acid. 



Another assertion made by Koch was that the comma- 

 bacilli are killed by acid, provided this be of the requisite 

 strength. While there can be no question after the detailed 

 experiments of Mr. Watson Cheyne that hydrochloric acid 

 of the strength of 0-2 per cent, kills without fail the comma- 

 bacilli, if allowed to act on them for a few minutes, I do not 

 hesitate to say that with the exception of the spores of 

 bacilli all other bacteria micrococci, bacteria, sporeless 

 bacilli, and vibriones and spirilla are alike killed under 

 similar circumstances by acid : of such strength. 1 And just 

 as a more dilute acid does not affect in a few minutes' action 

 the vitality of many other bacteria, so also the comma-bacilli 

 remain unaltered by it. I have mixed choleraic comma- 

 bacilli from a pure culture with a mixture of one part of 

 commercial hydrochloric acid in 1,000 parts of water for 

 from ten to thirty minutes, and on inoculating broth with 

 the medicated comma-bacilli I have obtained normal 

 growths of them. Other media known to have a noxious 

 effect on bacteria in general, have the same effect on 

 the choleraic comma-bacilli. The experiments of Koch 

 and also of Mr. Watson Cheyne ought, however, to be 

 accepted with a certain restriction after Dr. Macfadyan's 

 experiments carried out on the living animal. 2 Dr. 

 Macfadyan has shown that if a dog be kept without food 



1 Compare also a paper by Mr. Laws in the Report of the Medical 

 Officer of the Local Government Board, 1884. 

 * Journal of Anatomy and Physiology, vol. 21, 1887. 



