AMOEBAE A 



215 



have been able to cultivate the amoeba in vitro and noted in 

 some cases the excystation of the cyst contents as multinucleate 

 amoebae. 



This amoeba was first definitely recognized by Losch in 

 Russia in 1873. It is now known to have a wide geographical 

 distribution. The incidence of infection among man depends 

 mainly upon the sanitary conditions of the community, since 

 the infection is carried from man to man through cysts. Craig 

 estimates that ten per cent of the general population of the 



Fig. 85 Entamoebae of man. 



a-f. Entamoeba histolytica, a, a stained trophozoite (XIOOO); b, 

 stained precystic stage (XIOOO); c, a stained cyst (XIOOO); d-f, 

 excystation in culture (X700 after Yorke and Adams). 



g, h. Entamoeba coli. XIOOO. g, stained trophozoite; h, stained cyst. 



i-k. E. gingivalis. X500. i, j, living trophozoites; k, stained tropho- 

 zoite. 



United States harbor this organism. An acute infection by 

 Entamoeba histolytica is manifested clinically by dysentery. 

 In chronic cases, the host may void a number of infective cysts 

 without sulifering himself. Such a man is known as a "carrier." 

 The amoeba invades the liver also and causes in it various 

 abscesses of a serious nature. Numerous varieties are known. 

 Entamoeba coli (Losch) (Fig. 85, g, li). The amoeba varies 

 from 15 to 40 microns in diameter. Its cytoplasm is indistinctly 

 differentiated. Lobopodia are slowly formed and body move- 

 ment is sluggish. The endoplasm shows several food vacuoles 



