CROSS-INFECTION EXPERIMENTS 95 



that such a phenomenon interpreted by some as budding, does exist, 

 even though it is interpreted differently by other writers, and that 

 it is not restricted to a single genus. 



The characteristic dispersion of the karyosome in Council juania 

 is the most distinctive, constant characteristic of this amoeba, and 

 such dispersion is as a rule associated with trophozoites exhibiting 

 hyaline pseudopodia, while cysts exhibiting massed excentric karyo- 

 somes described for E. coli are, as a rule, associated with tropho- 

 zoites which form granular pseudopodia. 



If the differences in karyosome and pseudopodial formation 

 given for differentiating C. laflenri and E. coli are accepted, then 

 C. muris and E. ratti will be similarily differentiated. If, on the 

 other hand, the differences between E. coli and Cotmcilmania 

 lafleuri are eventually decided to be only racial in character rather 

 than generic, then C. muris and E. ratti become synonyms of 

 EndmnoBha muris. Further, the possibility must be considered that 

 the host-parasite relations of these amoebae of the rat and of man 

 are non-rigid. Kessel (1923a) established infections of E. coli 

 and of Councilmania lafleuri in rats and therefore indicates this 

 possibility. If such be true and the morphological differences 

 ascribed to E. coli, Losch, 1875, E. muris, Grassi, 1881, E. decii- 

 mani, Rudovsky, 1921, E. ratti, Kessel, 1924, and E. dipodomysi, 

 Hegner, 1926, be insufficient to differentiate them into species, then 

 the last four become synonyms oi E. coli. Further morphological 

 and experimental observations are needed before such conclusions 

 can be definitely made. 



Endamceba histolytica 



Lynch (191 5) records an epidemic of amoebic dysentery in rats 

 in South Carolina. His differentiation between the amoeba natural 

 to the rat and E. histolytica was not clearly made. Consequently 

 there is some doubt as to whether he was actually dealing with 

 E. histolytica. Brug (1919), however, records and figures an 

 amoeba from a wild rat in Java which appears without doubt to 

 possess the same morphological characteristics as E. histolytica of 

 man. Chiang (1925)^ in Harvard also records in rats natural in- 

 fections of an amoeba morphologically identical with E. histolytica 

 of man. Kessel (1923a) was able experimentally to infect rats with 

 E. histolytica of man and Chiang (1925) did the same thing. He, 

 however, carried the experimental work farther, recovered the 



