UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 20, No. 15, pp. 365-371 February 1, 1923 



A COMPARISON 

 OF THE CYSTS OF ENDAMOEBA COLI AND 

 COUNCILMANIA LAFLEURI IN CONGO RED 



BY 



NATHANIEL BERCOVITZ, M.D. 



Early in January, 1922, I conducted a series of experiments in 

 the protozoological laboratory at the University of California to 

 determine the permeability of the cysts of intestinal protozoan i^ara- 

 sites by a number of anilin stains. During the course of the experi- 

 ments it was noticed that there was no staining of the cysts by aqueous 

 solutions of the stains until one day a number of cysts of Council- 

 mania lafleuri Kofoid and Swezy were seen to appear red after being 

 exposed to Congo red. The next specimen contained cysts of Enda- 

 moeba coli, and exposure to Congo red showed no reaction in the 

 cysts which appeared clear in the red background. A third specimen 

 contained cysts of Councilmania and these also took the stain when 

 exposed to Congo red. This seemed to be unusual, so it was .decided 

 to make an intensive study of this phenomenon. At tirst it was 

 thought that this might be a quick way to differentiate between these 

 two types of amoeba, but as more eases were studied it was found 

 that the phenomenon was not constant. There were instances where 

 the Congo red had no effect on the cysts of Councilmania, and there 

 were instances where the Congo red stained cysts of Endamoeba coli 

 deeply. 



In order to arrive at some more accurate conclusion a series of 

 fifty cases was studied. Fresh solutions of Congo red, 1 per cent in 

 normal salt, were used throughout. The effect of this stain on every 

 type of cyst of human intestinal parasites available was studied, but 

 in the cvsts of Councilmania and Endamoeba coli only was there any 



