218 FAMILY: AMCEBID^ 



bodies are arranged at the periphery of the cyst in a tangential manner, 

 while leaving the central cytoplasm, which contains the nuclei, clear. 

 These acicular bodies were similar to certain bacteria which occurred in 

 the stool, and in shape resembled Charcot-Leyden crystals. The possi- 

 bility of their being parasitic in nature has to be considered, 



Schaudinn (1903) described a process of autogamy in the cyst of 

 E. coli. The nucleus of the encysted amoeba divided into two nuclei, 

 which took up positions at opposite poles of the cyst. Each of these 

 nuclei then gave ofi chromatin material into the cytoplasm, and then 

 divided to form two pairs of nuclei, one of each pair being a migrating 

 nucleus and the other a stationary one. The migrating nucleus of each 

 pair then passed across the cyst and united with the stationary nucleus 

 of the opposite pair. In this way a two-nuclear stage was again reached. 

 Each nucleus then divided, and the daughter nuclei repeated the division 

 so that a total of eight nuclei resulted. The writer (1907) observed 

 certain changes in the cysts of E. muris of mice which seemed capable 

 of a similar interpretation. The observations of Schaudinn have never 

 been confirmed, and it is abundantly evident that no such autogamy 

 process occurs in the development of the cysts of any entamoeba. The 

 eight nuclei undoubtedly result from straightforward repeated divisions. 

 Mathis and Mercier (1917) expressed the opinion that the usual type of 

 cyst with eight nuclei were gamete-producing cysts, which in the next host 

 liberated eight amoebae which conjugated in pairs. The cysts with a 

 larger number of nuclei were regarded as schizogonic cysts, which were 

 presumed to give rise to sixteen daughter amoebae which grew into adults 

 without conjugation. The figures they give are quite unconvincing, and 

 it is evident from their account that they have not produced sufficient 

 evidence in support of their view. 



PATHOGENICITY. — There is no evidence that E. coli can be pathogenic 

 to man. That infection is brought about by the ingestion of cysts was 

 demonstrated by Walker and Sellards (1913), who succeeded in infecting 

 seventeen of twenty men on whom experiments were conducted. The 

 infection gave rise to no symptoms, but cysts appeared in the stools in 

 one to eleven days. 



The many attempts made by the writer to infect animals with E. coli 

 have failed. In conducting such experiments it must be remembered that 

 many animals harbour amoebae of the E. coli type, and that they produce 

 cysts which cannot be distinguished from those of the human amoeba. 

 Kessel (1924a) reports the successful infection of monkeys with E. coli. 



Casagrandi and Barbagallo (1897) claimed to have seen the emergence 

 of amoebae from cysts which had been fed to cats. They supposed that 

 the cyst wall ruptured, and that eight amoebae escaped from the cyst. 



