x MODES OF DESTRUCTION OF B. PESTIS 293 



growth was added to the water so as to produce slight, though 

 distinct, turbidity. 



A single platinum loop of the watery emulsion yielded a very 

 large number of colonies of B. typhosus. 



a. To 50 ccm. of the typhoid water added 0*1 ccm. izal, 1 in 500. 



b. To 60 ccm. of the typhoid water added 0'1 ccm. izal, 1 in 600. 



c. To 75 ccm. of the typhoid water added 0*1 ccm. izal, 1 in 750. 

 After 5 minutes' exposure made cultures on agar and in broth 



with 3 loops. Incubation at 37° C. with the following result : — 



a. 1 in 500, 5 minutes' exposure : no growth in either tube. 



b. 1 in 600, 5 minutes' exposure : no growth in either tube. 



c. 1 in 750, 5 minutes' exposure : no growth on agar ; slight 

 turbidity of broth due to B. typhosus. 



This, then, agrees with experiment 1 5 as to complete disinfection 

 of B. typhosus by izal 1 in 600 in 5 minutes ; but as regards izal 

 1 in 750, the typhoid watery emulsion appears to be more amenable 

 to disinfection than the typhoid urine, for while in the latter good 

 growth appeared in the broth-tube, in the former the broth only 

 showed retarded and diminished growth of the B. typhosus. That 

 the slight turbidity of this broth was really due to B. typhosus was 

 proved not only by subcultures but by the positive agglutination 

 test, the bacilli becoming completely agglutinated by typhoid serum 

 (of a typhoid protected rabbit) 1 in 200 in 5 minutes. 



Comparing these experiments of watery emulsion of B. typhosus 

 with those of the typhoid stool the difference becomes obvious ; for 

 while izal 1 in 600 completely disinfected the watery emulsion in 

 5 minutes, and even as 1 in 750 greatly reduced the number of 

 bacilli in 5 minutes (no growth on agar, slight turbidity in broth), 

 in the typhoid stool (2) izal 1 in 600 did not disinfect in 15 

 minutes, though it succeeded in doing so in 30 minutes j in another 

 case (stool 9) izal 1 in 750 had no effect in 15 minutes, though it 

 caused complete disinfection in 30 minutes. 



Coming now to experiments of disinfection of culture 

 of B. pestis with cyllin, phenol, and formalin, I quote a 

 paper which I published in Public Health, June 1904 : — 



" The following experiments were undertaken to test 

 and compare the relative actions of ' cyllin,' ' phenol,' 

 and ' formalin ' on B. pestis of a virulent strain. This 



