E. histolytica: rabbits 



Lieberkiihn developed. The differences between the reac- 

 tions of two species of hosts (man and guinea-pig) to the 

 same parasite are strikingly brought out by these experi- 

 ments. Wagener and Thomson (1924) attempted to re- 

 peat these experiments without success. Since the colon of 

 the guinea-pig is 30 inches long they doubt if Chatton 

 obtained cecal infection by rectal injections. 



Rabbits. Huber (1909), until recently, was the only 

 investigator who claimed to have infected rabbits with 

 E. histolytica. Four of the 8 rabbits were positive. The 

 amoebae produced ulcers in the cecum but did not bring 

 on diarrhea or dysentery and were not passed in the feces. 

 Thomson (1926) has likewise succeeded in infecting 

 rabbits. Rectal injections of motile amoebae from cats 

 failed but one of 3 rabbits fed cysts of E. histolytica from 

 a chronic human case became infected and died 30 days 

 after the initial feeding. No cysts were observed in the 

 feces nor found at autopsy. The cecum alone was para- 

 sitized, and that invasion of the tissues occurred was 

 proved by the discovery of amoebae in the mucosa, sub- 

 mucosa and circular muscular layer. 



No doubt many other species of animals could be in- 

 fected with E. histolytica in the laboratory but probably 

 very few of these ever become parasitized in nature 

 except under extraordinary conditions. However, by 

 carefully performed experiments it may be possible to 

 determine why cysts hatch in one species of host and 

 not in another ; why newly hatched trophozoites are able 

 to live and multiply in one species of host and not in 

 another ; why one host becomes infected and another of 



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