LOESCHIA 



313 



In the same year there appeared papers by Wenyon and O'Connor 

 on the ' Human Intestinal Protozoa in the Near East/ detailing 

 the characters of E. histolytica, and by Chalmers and O'Farrall 

 with regard to its presence in the urinary tract, which brings in 

 the synonym Amceha urogenitalis Baelz, 1883. 



Wenyon and O'Connor consider that no infection can be ascribed 

 to L. histolytica unless some amoebae with included red corpuscles 

 are present or unless typical cysts are present in the stool. An 

 amoeba with retractile ectoplasm, and indistinct nucleus and active 

 movement, is most likely to be L. histolytica, but these characters 

 alone will not distinguish the organism. 



For the diagnosis of Amoebae they lay down the following rules : — • 



1. Amoebae containing red blood-corpuscles are L. histolytica, 



whether the stool is dysenteric or not; and, further, they 

 indicate an active dysentery. These cases urgently 

 require emetine treatment. 



2. Amoebae, none of which contain red blood-corpuscles, 



occurring in a dysenteric motion are indicative of L. coli 

 or oi L. histolytica in a carrier, while the cause of the 

 dysentery is not an amoeba; and these cases should be 

 watched for a few days, without treatment, with a view 

 to finding the cysts. 



3. Amoebae, none of which contain red blood-corpuscles, 



occurring in non-dysenteric motions may be L. coli or 

 L. histolytica, and diagnosis has to be -made by finding 

 the quadrinucleate cysts, perhaps, after several days' 

 observation. 



In 1918 Dobell showed, by experimental infection of tadpoles, 

 that L. histolytica and L. ranarum were distinct species, and with 

 Jepps drew attention to the existence of diverse races of L. histo- 

 lytica, which could be distinguished by the dimensions of the 

 cysts. 



The above does not complete the history, but is as full as space 

 permits, and we will now turn to the morphology. 



Morphology — -Vegetative Stage : Young Trophozoite Phase. — -This 

 phase may also be termed the histolytica phase, as defined above. 



It occurs when active dysenteric processes are proceeding in the 

 bowel, and is represented as a rule in the fresh condition by large 

 amoebae measuring from 30-90 microns in diameter, but exception- 

 ally being present in small size. As a rule its motility is very marked, 

 often starting with such a rapid action as to be worthy of the name 

 explosive. The pseudopodia are broad, and may be solely ecto- 

 plastic, or be composed of endoplasm as well. The ectoplasm may 

 be clearly distinguishable from the endoplasm even when the amoeba 

 is at rest, but often there is no such distinction. 



The cytoplasm may have a well-defined light green colour, or 

 more usually this colour is wanting. It may contain a number 

 of vacuoles, or it may not. It often possesses a number of ingested 



