ENTAMOEBA COLI 9I 



results. I do not believe it is possible to infect the cat with E. coli, or to 

 obtain any stages of development in this host. In the experiments 

 carried out with Dr. Dale in 1916 {vide Dale and Dobell, 1917) I studied 

 a number of kittens which had ingested the cysts of this species, but I 

 was unable to observe any development, and none of the kittens ever 

 acquired an infection. I found, on several occasions, that some of the 

 ingested cysts passed unchanged through the kitten's gut, and were 

 discharged in its faeces ; but a larger proportion degenerated and died 

 in transit, and I generally failed to find any forms — either cysts or 

 amoebae — in the faeces of kittens which had ingested cysts of E. coli. 



Conjugation. — At present there is no evidence of the existence of sexual 

 phenomena of any sort in the life history of E. coli. The " autogamy " 

 described in the cysts by Schaudinn (1903), and "confirmed" by severnl 

 later workers, was certainly a mistaken interpretation — as already noted. 

 " Conjugation " phenomena observed by other workers appear to be 

 equally speculative, and are hardly worth even mentioning. 



Mathis and Mercier (19176, d) maintain that the cysts ("gamogonic 

 cysts") of E. coli are of two sorts, — "macrocysts" and " microcysts," 

 distinguishable by their dimensions. They are supposed to liberate 

 macrogametesand microgametes respectively. The only concreteevidence 

 advanced in support of their view is a remarkable curve — based upon 

 measurements of only 100 cysts — incidentally mtroduced in one of their 

 papers (1917 b). The much more extensive series of measurements of 

 E. coli cysts made by Smith (1918) and Matthews (1919) have shown 

 conclusively that Mathis and Mercier's conclusions are not justified. 

 The dimorphism which they postulate in the cysts of E. coli does not 

 exist. My own measurements also show clearly that there is no evidence 

 of the existence of " microcysts " and "macrocysts." 



Whilst there is thus no direct evidence of the existence of a sexual cycle 

 in £. coli, it is by no means certain that conjugation does not occur. If 

 it does, then the probability is that it takes place between the young 

 amoebae recently issued from their cysts. To this extent I agree with 

 Mathis and Mercier. I originally suggested a similar possibility in the 

 development of E. rananini, and Mercier (1910) soon afterwards stated 

 that he had observed the whole sequence of events in Endamoeba blattae. 

 His observations supply the only real grounds for supposing that a 

 sexual cycle occurs in the development of any of the intestinal amoebae 

 of man or other animals. 



Cultivation. — E. coli has not been cultivated by any worker. It is 

 certain, and will be conceded by everybody acquainted with the subject, 

 that the " E. coli " cultivated by many of the earlier and some later 

 investigators {e.g., Fantham, 191 1), was in reality some free-living species 

 and not Entamoeba coli. 



Occurrence. — There is now so much information regarding the 

 occurrence of E. coli, and the facts are so generally recognized, that our 

 knowledge of the distribution of this organism can be dismissed in a 

 sentence. E. coli has been found living as a harmless commensal in the 

 colon of man wherever and whenever it has been sought : no race, nor any 

 country, has yet been discovered in which infections with this species 

 are not common. 



Treatment. — An E. coli infection cannot be eradicated by any known 

 method of treatment. Emetine, various intestinal disinfectants, and other 

 substances which have been tried are all inefficacious. There is a large 



