x MODES OF DESTRUCTION OF B. PESTIS 291 



Kesult : — 



a. After 1 5 minutes : agar free of growth ; broth free of 

 growth. 



b. After 30 minutes: agar has 1 colony (B. colli); broth free 

 of growth. 



c. After 1 hour : both tubes free of growth. 



From this it follows that izal 1 in 600 completely disinfected 

 the microbes of the coli-typhoid group in 1 hour ; but already in 

 30 minutes the reduction of all microbes was enormous, since only 

 the agar tubes showed one single colony, but it was not quite clear 

 whether B. coli or not. For practical purposes 30 minutes would 

 therefore suffice. 



Experiment 13. — The same stool (9) was used as above, izal 

 1 in 750. 



Result : — 



a. After 1 5 minutes : agar shows large number of coli-like 

 colonies ; broth clear. 



b. After 30 minutes : both tubes without growth. 



c. After 1 hour: agar shows 1 colony of sporing B. mesentericus. 

 The following Table III. summarises the results of all experiments 



made with typhoid stools in respect of the microbes of the coli- 

 typhoid group : — 



Table III 



