' 



304 A PARASITE OF AMCEBA 



to demonstrate, as they could not be stained 

 within the amoeba? sufficiently well to differentiate 

 them from broken-down bacteria, etc., and we 

 have found that the parasite itself readily breaks 

 up into granules and rapidly loses its stain. 

 Although we were able to infect healthy cultures 

 with a loopful of material from an infected tube, 

 the evidence for the existence of a parasite was 

 not yet conclusive. Fortunately while examining 

 some films containing infected amoebae by the 

 jelly method, a zooglcea mass was noticed com- 

 posed of large cocci-like bodies, and, since these 

 had not occurred during the bacteriological analyses 

 of healthy cultures, it was decided to isolate them. 

 Colonies on plates were accordingly prepared, 

 and a pure culture (fig. 33) made on a nutrient 

 agar slope. With this pure culture of the para- 

 site we have been able to infect healthy pure 

 mixed cultures of the amoeba, and find the usual 

 appearances of degeneration and death and com- 

 parative absence of encystment as in the original 

 tubes. Steps are now being taken to try to 

 infect with this parasite a culture of amceba from 

 dysenteric stools kindly sent to us by Dr. J. W. 

 Stephens, of Liverpool, and it is also proposed 

 to find out if the parasite will destroy other 

 protozoa, particularly the pathogenic varieties. 1 



1 While this volume was in the press we have been able to infect, 

 with the parasite, cultures of an amoeba obtained from pond water and 

 apparently also cultures of two flagellates, namely, Potytoma granulosa 

 and Bodo grandis. Bodo saltans appears to be unaffected by it. We 

 think the injurious effect of the parasite is due to some intracellular 

 poisonous substances, since the parasite will only destroy those 

 organisms which actually ingest it. We have so far been unable to 

 kill the amoebae with extracellular products. 



