196 FAMILY: AMCEBIDiE 



a ragged appearance, and to it bacteria and other debris may adhere. 

 This type of movement is common in certain free-living amoebas, and 

 from it the name " Umax " is derived. Though occasionally E. coli will 

 be seen to move with an activity almost, if not quite, equal to that of 

 E. histolytica, this is rarely the case, and the energetic movements of 

 E. histolytica serve as one of its most important distinguishing features. 

 When degeneration is advanced the movements become less evident, and 

 finally cease altogether, though very often evidently degenerate amoebae 

 will commence moving with remarkable activity when warmed on the 

 warm stage. In the formation of the pseudopodia the first indication is 

 a slight elevation of the ectoplasm, but as this increases in size the endo- 

 plasm quickly flows into it. A characteristic appearance of E. histolytica, 

 as seen in the stool, is that of an amoeba with a clear, broad, hyaline 

 ectoplasm sharply marked off from a granular endoplasm. Such forms 

 may be producing pseudopodia with great activity, and these frequently 

 consist entirely of ectoplasm. This extreme condition is probably the 

 result of degeneration. As E. coli does not produce appearances of this 

 kind, the marked ectoplasm of these altered E. histolytica serves as a dis- 

 tinguishing feature. In the perfectly fresh and normal individuals the 

 distinction between ectoplasm and endoplasm is much less marked. The 

 writer has examined portions of infected mucosa removed through the 

 sigmoidoscope. Though not more than one minute had elapsed after 

 removal, the amoebae could be seen actively motile within the pieces of 

 mucosa and forming ectoplasmic pseudopodia, as in the freshly passed 

 dysenteric stool. It hardly seems possible to regard the amoebae under 

 these conditions as being in any way degenerate. On the other hand, 

 the appearance of an amoeba with a relatively thick ectoplasm surrounding 

 a globular mass of granular endoplasm is undoubtedly due to a degenera- 

 tive change. The endoplasm has a ground-glass appearance, and, apart 

 from the nucleus and food vacuoles, contains, according to Dobell (1919), 

 numerous small granules which stain intra vita^n with neutral red. The 

 food vacuoles include red blood-corpuscles (Fig. 95, i), and sometimes 

 leucocytes or other cells in various stages of degeneration (Fig. 95, i). 

 Sometimes the whole endoplasm appears packed with red cells, and in 

 many cases, as these become dehsemoglobinized, the cytoplasm assumes 

 a yellowish tint. It is only rarely that other objects are ingested by the 

 amoebae. The number of amoebae in any particular specimen containing 

 red blood-corpuscles varies considerably. Sometimes as many as 25 per 

 cent, will show them, while in other cases a long search will reveal only 

 a single one, or none at all. Amoebae containing red cells may be found 

 in stools which do not show any blood or other abnormality on naked-eye 

 inspection. 



