300 ORIENTAL PLAGUE chap. 



Taking a certain dilution of carbolic acid as being 

 capable of completely disinfecting in five minutes B. pestis 

 of culture, the figures of carbolic coefficient for cyllin and 

 izal work out something like 24 to 30 for cyllin, 22*5 to 

 26 '6 for izal. It will be seen from this that cyllin and 

 izal leave phenol, and still more formalin (when used in 

 fluid form) far behind, and, with the exception of 

 bichloride of mercury, are more powerful disinfectants 

 than certain disinfectants which, when tested under 

 similar conditions on non-sporing microbes, have a co- 

 efficient inferior to phenol. Although I have made no 

 special experiments on B. pestis with chloros, kerol, or 

 other agents, either belonging to the group of strong 

 oxidisers or to the group of tar products, judged by what 

 these substances are capable of effecting when tested on 

 B. typhosus I have no doubt that they will be found 

 powerful disinfectants also for B. pestis. 



Be it added here that although the figures given here 

 of phenol, formalin, cyllin, and izal apply to experiments 

 on watery emulsions of pure culture of B. pestis, it does 

 not follow that they apply in exactly the same degree if 

 disinfection is performed on plague organs direct, such as 

 would have to be dealt with in actual practice. For 

 under the latter conditions the relations of disinfectant to 

 infective material, i.e. open and free contact of the 

 disinfecting fluid with the B. pestis contained within the 

 viscid and gelatinous albuminous materials — blood, intes- 

 tinal contents, sputum, viscera, — may be, and probably are, 

 different from what they are when watery emulsions of pure 

 cultures are used. Moreover, the degree of efficacy of one 

 as compared with the other disinfectant may be altered. 

 Not that cyllin and izal, chloros and kerol, and some 



