10 MANUAL OF HUMAN PROTOZOA 



a rapid flowing-out of the grayish granulated endoplasm. 

 The amoebae vary in diameter 15-35ij. The monopodal 

 individuals may be longer. On a warm stage, the activity 

 may continue for hours if the cover-glass is sealed to the 

 slide by vaseline or paraffin. But sooner or later, the amoeba 

 will become less and less active and assumes a more or 

 less rounded form. The formation of the pseudopodia and 

 change of body form may continue for some time. Finally 

 the organism becomes immobile. With the decrease in 

 activity, the ectoplasm and endoplasm may often become 

 more clearly difterentiated in many individuals. The ecto- 

 plasm may be more voluminous than before, while the 

 endoplasm becomes alveolated. In the endoplasm are 

 found a nucleus and food particles. The nucleus is seldom 

 seen in actively moving amoebae, but may be faintly seen 

 as a ring of small granules, about 5m in diameter, in slug- 

 gish individuals. The food consists of host tissue cells and 

 tissue and body fluids which are absorbed through the 

 body surface. The amoeba takes in erythrocytes and frag- 

 ments of tissue cells, which give the organism a charac- 

 teristic appearance. The number of erythrocytes found in 

 an individual varies a great deal and not all individuals 

 contain them. Bacteria and other microorganisms which 

 are freely taken in by other species of Entamoeba men- 

 tioned in the following pages, are only seldom engulfed 

 by E. histolijtica. 



2. Stained specimens. When fixed and stained (p. 58), 

 the trophozoites (Fig. 1, ^-4) appear more or less rounded 

 and their cytoplasm is reticulated. In some individuals the 

 cytoplasm may be differentiated into the clearer ectoplasm 

 and denser endoplasm (Fig. 1, 3). The erythrocytes pres- 



