HOST-PARASITE RELATIONS: INTESTINAL PROTOZOA 



amoebiasis in kittens when they used amoebae from an 

 acute case but only one of 14 kittens became infected 

 when motile amoebae from a chronic human case were 

 injected into the rectum; this single case developed into 

 a chronic infection which was difficult to transfer to 

 other kittens and exhibited no lesions on autopsy. 



(2) Resistance to drugs. Many cases have been 

 described in the literature of drug resistant strains of 

 E. histolytica. An attempt was made by Dobell and Laid- 

 law (1926a) to determine whether this species when 

 grown in culture is able to build up a resistance to emetin. 

 A strain that survived a medium containing emetin in 

 dilution of i to 50,000 was subcultured in a similar 

 medium for over a month, and also in media containing 

 larger amounts of emetin. The cultures were kept going 

 in the i to 50,000 dilution only with difficulty; no con- 

 tinued growth was obtained in media of greater emetin 

 concentration; and no evidence was obtained of an in- 

 crease in resistance to the drug. These investigators 

 believe that "emetin-resistant" cases of amoebiasis are 

 not due to a resistant strain of amoebae but are the result 

 of some physiological idiosyncrasy of the host that pre- 

 vents the emetin from reaching the large intestine, pos- 

 sibly being excreted in the urine, as appears to be true 

 when the drug is administered to cats. That differences 

 may exist, however, as regards sensitiveness to emetin 

 in strains both from man and monkey was noted by these 

 investigators; one human strain was more sensitive to 

 the drug than the other, and this was true also of the 

 two monkey strains used. 



Kofoid and Wagener (1925) also report studies with 

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