PROTOZOA IN THE DIGESTIVE TRACT 27 



It is widely distril)uted, ])ut iisuallv of rare occurrence, 

 aldiough in certain areas the infection rate seems to he 

 high. It has been seen only in the trophic stage in dysen- 

 teric or diarrhoeic faeces, and encysted forms haye not yet 

 been found. 



Trophozoites 



1. Living specimens. This actiye amoeba (Fig. 6, !> -) 

 undergoes progressive moyement by forming a few broad 



/ 2 3 4 5 



Fig. 6. Dientamoeba jragilis. X 1150. (original) 

 1, 2. Living trophozoites. 



3. A stained uninucleate amoeba. 



4, 5. Stained binucleate amoebae. 



and thin pseudopodia. The cytoplasm is well differentiated 

 in actiyely moving individuals. The endoplasm is highl\' 

 granulated and contains cocci or bacilli in food vacuoles. 

 The nucleus is ordinarily faintly visible. The amoeba meas- 

 ures 4-18m in diameter, but the majority are 5-12^ in 

 diameter. 



2. Stained specimens. The body is elongate round. The 

 cytoplasm is reticulate and bacteria occur in food vacuoles. 

 The amoebae (Fig. 6, 3-5) possess one or two nuclei. The 

 ratio of uni- and bi-nucleate forms varies among different 

 faecal specimens. In some binucleate forms may be 80% 

 or more, while in others uninucleate forms may be pre- 

 dominant. The nucleus is a small vesicle and about 1-2. 5m 



