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Mr. A. G. K. Foulerton and Dr. A. M. Kellas. [Mar. 30, 



moreover, it appeared probable that in addition to the action of peroxide of 

 hydrogen there might be another factor at work, for a consideration of the 

 chemical decomposition by which the peroxide was produced suggested the 

 simultaneous liberation of quantities of nascent hydrogen which would 

 doubtless also exercise a powerful germicidal action. 



Assuming, however, that the germicidal action of peroxide of hydrogen was 

 the main factor concerned, we found that some experiments which we carried 

 out to test the comparative resistance of the bacteria used in the experiments 

 to the action of the peroxide gave results which were roughly in accordance 

 with those detailed in Table VI. We found that sporing cultures of 

 B. anthracis were strongly resistant ; experiments carried out at temperatures 

 of 0° C, 15° C, and 26° C. with a 1-per-cent. solution of peroxide of hydrogen 

 showed that with 30 minutes' immersion no obvious effect on the bacteria was 

 produced at any of the temperatures, with 60 minutes' immersion no effect 

 was produced at a temperature of 15° C, but there was distinct inhibition of 

 subsequent growth in experiments carried out at 26° C, whilst the bacteria 

 were destroyed after 120 minutes' immersion at all three temperatures. 

 With regard to the non-sporing bacilli, we found that B. prodigioms and 

 B. pyocyaneus were more resistant to the peroxide than B. coli communis, 

 B. dysenterice, and B. typhosics, the last mentioned being readily destroyed by 

 very dilute solutions, and B. prodigiosus exhibiting a marked degree of 

 resistance. In the performance of these experiments it was noted that the 

 rapidity of the decomposition of the peroxide in the solution, and the conse- 

 quent activity of germicidal action, appeared to depend to some extent upon 

 individual peculiarities in the chemical constitution of the various species 

 used in the tests. The experiments were carried out by introducing definite 

 quantities of cultures of each species from nutrient agar into test-tubes con- 

 taining the diluted peroxide and kept at the several temperatures. And it 

 was apparent that the rapidity with which the peroxide was decomposed, as 

 measured by the evolution of oxygen in bubbles from the solution, varied 

 widely with different species at the same temperature ; for any one species 

 the evolution of gas was more rapid at the higher temperature, with 

 corresponding intensity of germicidal action. 



In these experiments to test the germicidal action of solutions of peroxide 

 of hydrogen, a special effect of the peroxide in temporarily inhibiting the 

 formation of pigment by chromogenic bacteria which had been immersed in 

 solutions of it was also noticed. Thus, after an immersion for 60 minutes in 

 a 1 in 500 solution of peroxide of hydrogen kept at a temperature of either 

 15° C. or 26° C. the amount of subsequent growth of B. prodigiosus was in no 

 way affected ; but whereas in control cultures of the bacillus which had not 



