290 ORIENTAL PLAGUE chap. 



disinfection of the microbes of the coli-typhoid type as well as of 

 the streptococci. (Control experiments made of this stool in high 

 dilution by means of Drigalski and Conradi plates showed : 1 6 

 millions B. coli, 2 millions B. typhosus, and about 10 millions 

 streptococci per 1 ccm.) 



Experiment 9. — The same stool (5) as used in experiment 8 was 

 treated with izal 1 in 600. 



Result : — 



a. After 1 5 minutes : agar, no growth ; broth, no growth. 



b. After 30 minutes : agar, no growth ; broth, no growth. 



c. After 1 hour : agar, no growth ; broth, no growth. 



From this it follows that izal as 1 in 600 completely disinfected 

 in 15 minutes. 



Experiment 10. — The same stool (6) as in experiments 8 and 9, 

 izal 1 in 750. 



Result : — 



a. After 1 5 minutes : agar shows 2 colonies (B. coli) ; broth 

 uniformly turbid (B. coli). 



b. After 30 minutes : agar, no growth ; broth uniformly turbid 

 (B. coli). 



c. After 1 hour : both cultures free of any growth. 



From this it follows that izal as 1 in 750 completely disinfected 

 in 1 hour, but not in 30 minutes. 



Experiment 11. — Semi-solid stool (7) of a case of typhoid, 10th 

 day of illness. Added 1 gramme to 50 ccm. of sterile distilled water. 

 (From this dilution, 1 in 50, made with one loop an agar culture, 

 with the result that after incubation the agar surface was covered 

 with innumerable colonies, in many cases confluent.) To the above 

 dilution, 1 in 50, added 0'1 ccm. izal, that is 1 in 500. Cultures 

 from the medicated fluid were made after 15 and 30 minutes and 

 after 1 hour, using for each culture tube 3 loops. 



Eesult : — 



a. After 15 minutes : agar shows 1 colony of sporing B. mesen- 

 tericus ; broth- tube turbid, due to cocci and streptococci (no bacilli). 



b. After 30 minutes : both tubes free of growth. 



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



In this experiment, then, izal 1 in 500 disinfected the microbes 

 of the coli-typhoid group in 15 minutes, though not those of cocci. 



Experiment 12. — The same stool (8) was used as above, izal 

 1 in 600. 



