E. HISTOLYTICA CYSTS! CHEMICALS 



them in 15 minutes or less; formalin i per cent, destroyed 

 them ; in sodium hydroxide they became swollen at once ; 

 death seemed to follow treatment with chlorinated lime, 

 I per cent, bichloride of mercury, i per cent, and carbolic 

 acid ; and lysol, i per cent, killed quickly not only cysts of 

 E. coli and C. lafleiiri but also those of E. histolytica. 

 The conclusion seems justified that these various disin- 

 fectants are powerful destructive agents for amoeba 

 cysts ; and it seems probable that those of E. histolytica 

 are at least as susceptible as are the cysts of the two 

 species principally studied. As Bercovitz suggests, how- 

 ever, culture experiments in addition to the eosin and 

 hematoxylin tests, are necessary to prove that the cysts 

 were really destroyed. 



The culture method was employed by Kessel (1925b) 

 in his study of the effects of chlorin water on cysts of 

 Hartmannella hyalina. No excystation occurred in cul- 

 tures within 72 hours after the cysts had been subjected 

 for 10 minutes to chlorin water containing free chlorin of 

 from 2.2 to 4.0 per cent, and very few cases of excysta- 

 tion were noted until a dilution of 0.4 per cent was 

 reached. No excystation took place in cysts kept in 0.2 

 per cent chlorin water for 24 hours, and none in 0.15, 

 0.1, and 0.08 per cent chlorin water for 48 hours. Cysts 

 did not hatch after 96 hours in 0.06 per cent chlorin 

 water, but a few excysted in 0.009 per cent and many in 

 0.006 per cent chlorin water. 



The culture method was also used by Yorke and 

 Adams (1926b) in their studies of E. histolytica. The 

 cysts were subjected to the chemical and then washed 

 and placed in culture medium. They found them very 



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