The trophozoites of E. histolytica, E. coli and E. nana and of Dientamoebae fragilis have been observed in aqueous smears and the essential findings recorded. Material for a similar study of the trophozoites of Iodamoeba butschlii has not been available. The observations indicate that certain features in the morphology of the amoebae can be demonstrated in the aqueous medium, such as (1) the distensibility of the ectoplasm of the E. histolytica, (2) the relative fragility of the ectoplasm of the E. coli and E. nana, (3) the resiliency of the ectoplasm of the Dientamoeba fragilis, (4) the remarkable strength of the nuclear membrane of the E. histolytica and E. coli.
Some of these characteristics together with the visibility of the nuclei help to differentiate the species of amoebae in the human stool.
It also has been recorded that the annoyance of Blastocystis hominis can be eliminated by the use of the aqueous smear.
I have been unable to find any reference in the literature to the use of aqueous smears in the study of the amoebae of man. However, it does not seem possible that such a simple procedure has not been used by some workers.
It is my pleasure to acknowledge the generous and valuable advice of Dr. C. M. Johnson, protozoölogist at the Gorgas Memorial Laboratory and the efficient assistance of J. F. Buckner and H. A. Down of the Hospital Corps, U. S. Navy.
Lieutenant Commander, Medical Corps, United States Navy.