366 CLINICAL BACTERIOLOGY. 



intussusception. The ameba sends out processes pseudo- 

 pods around the foreign body, and in a certain sense thus 

 surrounds it. Nothing is yet known with certainty as to 

 the need of oxygen on the part of the amebae. 



Propagation of the amebae probably takes place by 

 dichotomous division, although direct division of cell and 

 nucleus has not yet been observed. Spore-formation, such 

 as has been assumed by some, has thus far not been dem- 

 onstrated. Of importance are certain permanent forms, 

 which have acquired especial resistance as a result .of en- 

 capsulation ; these are designated permanent cysts or en- 

 cysted amebae. They are generally small from 10 to 12 fJL 

 long have a much sharper, at times distinctly double, 

 contour, and possess a translucent luster. The nucleus is 

 only indistinctly recognizable. In form the bodies are 

 round, and they are nonmotile. 



Death of the amebae is manifested principally by cessa- 

 tion of movement, the greater or lesser activity of which 

 also is an expression of a corresponding degree of vitality. 

 With the advent of loss of motility the ameba invariably 

 assumes a round shape, the differentiation between ecto- 

 plasm and entoplasm disappears, and the nucleus becomes 

 distinctly visible. The dead amebae after a time undergo 

 degeneration : either they become homogeneous, with a 

 fat-like luster, or they disintegrate into granules, often 

 after having become constricted into several round masses. 

 In cover-slip preparations the amebae, after cessation of 

 movement that is, after death do not remain visible for 

 more than two days ; in the stools they have already dis- 

 appeared within twenty -four hours ; only the encysted 

 forms persist for a longer time, being still distinctly recog- 

 nizable after twenty days in cover-slip preparations, as well 

 as in preserved stools, but no longer after four weeks 

 (Quincke). 



The resistance of the amebae to thermal and chemic in- 

 fluences has been but little investigated. The most suitable 

 temperature is that of the body. Outside of the organism 

 the parasites rapidly lose their motility, which at room-tem- 

 perature is lost after the lapse of a few hours exceptionally 

 eight hours, and in one instance twenty-four hours. Ele- 

 vation of the temperature to that of the body (examination 

 upon a warm stage) increases the motility and conduces to 

 the survival of the amebae for a longer time. It has, how- 



