446 



PROTOZOOLOGY 



Genus Entamoeba Casagrandi and Barbagallo (1895). Nucleus 

 vesicular, with a comparatively small endosome, located in or near 

 the center and with varying number of peripheral nonchromatinic 

 granules attached to the nuclear membrane (Fig. 187, b) ; chromatin 

 in the endosome and in peri-endosomal region. The genus was es- 

 tablished by the two Italian authors who were unaware of the ex- 

 istence of the genus Endamoeba (p. 444). Numerous species in ver- 

 tebrates and invertebrates; one species in Protozoa. 



Fig. 189. a, Endamoeba majestus, X420 (Kirby); b, E. simulans, X420 

 (Kirby); c, Entamoeba paulista in Zelleriella, X290 (Stabler and Chen). 



E. histolytica Schaudinn (1903) (Figs. 190, 191). The trophozoite 

 is an active amoeba and measures 7-35 (9-20) n in diameter; cyto- 

 plasm usually well differentiated; eruptive formation of large lobo- 

 podia, composed largely of ectoplasm; when fresh, active monopodal 

 progressive movement; the vesicular nucleus appears in life as a 

 ring, difficult to recognize; food vacuoles contain erythrocytes, tissue 

 cell fragments, leucocytes, etc.; stained nucleus shows a membrane, 

 comparatively small peripheral granules, a centrally located small 

 endosome and an indistinct network with a few scattered chromatin 

 granules. The trophozoite multiplies by binary fission. The amoeba 

 lives in the lumen and in the tissues of the wall of the colon, and 

 brings about characteristic ulceration of the colon which is typically 

 accompanied by symptoms of amoebic dysentery. Through the portal 

 vein, the amoeba may invade the liver in which it produces abscess, 

 and other organs such as lung, brain, testis, etc. The infection in 

 these organs is referred to as amoebiasis. 



Under certain circumstances not well understood, the amoebae 

 remain small after division. Such amoebae are sluggish and known 



