94 HUMAN INTESTINAL PROTOZOA IN THE NEAR EAST 



Summary of Matter discussed in Part II. 



(1) It is often quite impossible to distinguish unencysted forms 

 of E. histolytica from E. coli. The cysts, however, can be dis- 

 tinguished. Accordingly, it is safer to diagnose E. histolytica only 

 if the amoebae contain red blood corpuscles or if definite four-nuclear 

 cysts are present. Some rules to act as a guide to the diagnosis of 

 intestinal amoebae are given. 



(2) The cysts of E. histolytica vary greatly in size. There occur 

 certain strains of E. histolytica with cysts 7 to 10 microns in 

 diameter, strains with cysts of intermediate size and finally large 

 strains with cysts 15 to 19 microns in diameter. 



(3) There is no doubt that the presence of the four-nuclear cyst 

 is an indication of infection with E. histolytica, even when there has 

 been no history of previous dysentery. The cysts from carriers who 

 have never suffered from dysentery rnay give rise to acute amoebic 

 dysentery in kittens. 



(4) Cases may remain infected with E. histolytica for years. 

 There are in these cases periods of acute dysentery, when amoebae 

 with included red cells are present in the stool, alternating with 

 periods of comparative health when only small amoebae and cysts 

 are passed. Cases may remain as healthy carriers for long 

 periods without showing any signs of dysentery. It is probable 

 that these healthy carriers really have some ulceration of the 

 large intestine, which, however, is not so extensive as that in the 

 acute dysenteric. 



E. histolytica may establish itself in the gut with the production 

 of true dysentery or without the production of any symptoms what- 

 ever. In the removal of new troops from England to areas in 

 which amoebic dysentery is not endemic it is inadvisable to station 

 them, even for a short time, in centres of amoebic dysentery like 

 Egypt unless urgent military requirements leave no other 

 alternative. 



(5) The bacillary dysentery stool when seen at the height of 

 infection is characteristic, both macroscopically and microscopically, 

 and can be recognized by its general appearance and by the extra- 

 ordinary cellular exudate when viewed under the microscope. The 

 amoebic dysentery stool contains darker blood and mucus but cannot 

 be recognized with certainty apart from the amoebae. There is 

 absence of the cellular exudate of the bacillary dysentery mucus. 



(6) The characters of the unencysted E. coli are so indefinite 

 as to render its identification, apart from the cysts, most difficult. 

 We have obtained no evidence that E. coli can ingest red cells. 



