Fig. 60.—The more important intestinal amoebae of man showing nuclear structure when stained. 1. E. histolytica. 1(a). E. histolytica cyst. 2. E coli. 2(a). E. coli cyst. 3. E. nana. 3(a). E. nana cyst. 4. I. bütschlii. 4(a). I. bütschlii cyst. (After Dobell.)
The histolytica nucleus has a thin nuclear membrane and is poor in chromatin while the tetragena nucleus has more chromatin, showing radial projections from the inner surface of the nuclear membrane, and a loose central spherical karyosome, which contains a central chromatin dot or centriole, with a clear halo surrounding it. Dobell states he has not been able to note this centriole.
The preëncysted E. histolytica has a nucleus resembling that of E. coli. The smaller size and chromidial bodies are differentiating.
Animal experimentation upon kittens with E. coli by Schaudinn, Craig and Wenyon have been unsuccessful as to production of dysenteric manifestations. On the other hand all of these experimenters produced typical lesions and dysenteric manifestations in kittens injected rectally or fed with material containing pathogenic amoebae.
Wenyon as previously stated produced a liver abscess in one of his experiments.
Darling has been so successful in his experimental work with kittens that he compares the colon of a kitten to a test tube and suggests the procedure of rectal injections of material containing amoebae as a means of differentiating the two human amoebae.
On the other hand Walker was unable to infect kittens and monkeys with material containing pathogenic amoebae and he makes the statement that such failures would indicate the greater susceptibility of man to infection, as he was able to infect 17 out of 20 men with one feeding of such material.
Sellards and Baetjer note that inoculation of kittens per rectum or by feeding dysenteric stools rich in amoebae has resulted in infection in about 50% of experiments.
By inoculating the material directly into the caecum they were able to infect every one of their kittens. They were also able to propagate a strain of amoebae through a series of animals for several months.