82 AMOEBAE LIVING IN MAN 



"schizogony" is apparently a suitably-posed group of 8 individuals of 

 E. nana. 



More recently, Mathis and Mercier (1917 d) have attempted to show 

 that E. coli forms two kinds of cysts — "schizogonic " and " gamogonic." 

 The latter will be considered later. In the former, they believe that the 

 nucleus divides repeatedly until 8 to 16 are present in the cyst. The 

 nuclear multiplication may take place partly in the amoeboid condition ; 

 and nuclei of variable size are often found, which are believed to 

 reproduce by budding. The fully-formed cysts vary from 14 /u. to 26 /z 

 in diameter, but measure usually 17 /x. Their protoplasm may contain, 

 even within the fully formed cysts, the remains of ingested food ; and 

 it is stated to be more alveolar, vacuolate, and eosinophile than that of 

 the ordinary (" gamogonic ") cysts. At the end of the period of nuclear 

 multiplication, the protoplasm segments, the cyst bursts, and a brood of 

 small amoebae is liberated. All this is said to occur in the same host, 

 as a normal process of auto-infection. 



I have never seen anything resembling this process, although I have 

 studied a very large number of E. coli infections. I have, however, seen 

 most of the forms which Mathis and Mercier interpret in this manner. 

 Measurements of the cysts give no support whatever to their belief that 

 there is a dimorphism of the type which they describe. Smith (1918) 

 and Matthews (1919) have shown conclusively that it does not exist, and 

 my own observations are entirely in agreement. The cysts with more 

 than 8 nuclei, and with nuclei of unequal size, are, in my opinion, 

 abnormalties. They do not occur in every infection, and similar nuclear 

 abnormalities may be found in E. histolytica — a species in which they 

 admit that no schizogony occurs. The "foreign bodies" in the 

 "schizogony cysts" are merely small chromatoid bodies, such as so 

 frequently occur in E. coli cysts — notwithstanding that Mathis and 

 Mercier deny that they are ever found in this species. And their 

 " amoebae " with more than one nucleus are merely, I believe, irregularly 

 shaped cysts such as one often meets with in E. coli infections.* 



One naturally attaches much importance to the statement of Mathis 

 and Mercier that they have seen the emergence of the broods of small 

 amoebae from their "schizogony cysts." On this point their words are 

 unequivocal. Not only do they say that it is "not rare" to find this 

 process taking place in fresh stools, but they also state that they have 

 watched the living amoebae emerge. Their only figuref of the process, 

 however, is highly unconvincing. The formation of the 8 young 

 amoebae is not shown — merely a body, supposed to be a cyst of E. coli, 

 with 4 small amoebae. Two of these are depicted within the cyst, and 

 two without ; and their nuclei are strikingly different from the nuclei 

 which the authors figure in the earlier stages. Mathis (1913) had 

 previously figuredij: a similar stage, which it is interesting to compare. 

 One would be tempted to think that both figures were drawn from the 



* Casagrandi and Barbagallo were misled, I believe, in the same way by these 

 cysts — as several other workers have also been since. Irregular cysts may easily be 

 mistaken for amoebae in stained preparations, because — as shown elsewhere (Dobell 

 and Jepps, 1918) for E. histolytica — the cyst wall becomes invisible when the cyst is 

 mounted in balsam. 



t Vide Mathis and Mercier (1917^, fig. 15. 



X Vide Mathis (1913), PI. II, fig. 16. 



