150 HUMAN INTESTINAL PROTOZOA IN THE NEAR EAST 



from amoebic dysentery either after inadequate or ineffective treat- 

 ment or after no treatment at all. If the cysts from such cases 

 find their way into the water supply or into moist food without 

 having been dried they are likely to give rise to outbreaks of 

 /amoebic dysentery, so that any agent like a fly which brings about 

 their distribution must be regarded with suspicion. 



(A) EXPERIMENTS WITH HOUSE-FLIES (MuscA AND FANNIA). 



(1) Do the Flies ingest the Cysts ?-*-Kuenen and Swellengrebel 

 (Cent, of Bakt., Bd. 71), working in Sumatra, showed that flies 



x'ingested cysts of E. histolytica when they fed on infected fseces. 

 point w readily confirmed by allowing flies to feed on 

 faeces containing cysts and dissecting the flies shortly after.* We~ 

 found in every case that the gut contained faeces and that in this 

 faecal material in all parts of the intestine of the fly the cysts 

 occurred just as they had done in the specimen of faeces on which 

 the flies had fed. We were able to demonstrate also that the flies 

 ingested in a similar manner the larger cysts (fifteen to twenty-five 

 microns) of the non-pathogenic human entamoeba, E. coli, and the 

 cysts of the flagellate Lamblia intestinalis. % 



(2) Survival of the Cysts in the Intestine of the Fly.-PK.uenen 

 and Swellengrebel stated that the cysts quickly degenerated in the 

 fly's gut and soon became unrecognizable. We dissected flies at 

 various intervals after feeding and noted that so long as fasces were 

 present in the gut cysts could be found, but that they vanished 

 with the disappearance of the faeces from the flies' intestines. 

 Cysts of E. histolytica, E. coli and Lamblia intestinalis were all 

 found in the intestine twenty-four hours after the last feed on faeces. 

 After this time the flies have generally emptied their gut of faeces 

 and then no cysts could be discovered.^ In one instance cysts of 

 E. coli were found in the gut so long as forty-two hours after the 

 last feed. The question of the vitality of these cysts is discussed 

 below, but it may be remarked here that from their normal and 

 living appearance after their sojourn in the fly there can be no doubt 

 that the majority were still alive and therefore infective. Further- 

 more we have observed the passage through the intestine of the fly 

 of living and active Trichomonas. The application of the eosin 

 test, to be described below, also lent support to this view. 



* Captain J. G. Thompson, R.A.M.C., informed us that he had made a similar 

 observation that flies were able to ingest the cysts. 



