634 Dysentery 



1. Entamoeba Coli (Losch, 1875). — ^This organism seems to be a 

 harmless commensal, living in the intestines of man, many domestic, 

 and many wild animals. It may be abundant when the reaction 

 of the intestinal contents is neutral or alkaline. It usually measures 

 between 10 and 20 ^ in diameter when free, but when encysted from 

 15 to 50 ix. It is spheroidal when not in motion, and under these 

 conditions it is difficult to differentiate endoplasm and ectoplasm. 

 The ameboid movement is sluggish and the pseudopods are rather 

 short, broad, and blunt. As they are protruded the clear ectoplasm 

 becomes visible. The organism has a grayish color, a finely granular 

 cytoplasm, and usually only a single vacuole. The nucleus is usually 

 fairly well defined and spherical, and, in addition to the chromatin, 

 contains several nucleoli. When stained with polychrome methy- 

 lene-blue the ectoplasm stains blue; the endoplasm, violet; and the 

 nucleus, red. 



Reproduction usually takes place by simple division, but a form 

 of autogamous sporulation also takes place, the organism first be- 

 coming encysted, the nucleus dividing into eight segments, and 

 the whole process eventuating in the formation of eight young 

 organisms. 



This ameba is easily cultivated upon artificial media according 

 to methods to be described below. 



It is not pathogenic, and all attempts to make it damage the 

 intestines of experiment animals have failed. 



2. Entamoeba Histolytica (Schaudinn*). — This is now recognized 

 as the organism seen by Losch, Koch, Kartulis, Councilman and 

 Lafleur, and accepted as the cause of the amebic form of dysentery. 

 It is found in all parts of the world, but more frequently in tropical 

 than colder climates, and is present only in the intestines of those 

 suffering from dysentery. It is usually present in great numbers 

 so that its discovery in the evacuations is easy. 



Morphology. — It is usually considerably larger than Entamoeba 

 coli and varies in diameter up to 50 /i. When at rest it is spherical, 

 when active it is very irregular. Its movement is active and the 

 pseudopodia are larger and more numerous than in the other species. 

 The differentiation of ectoplasm and endoplasm is usually distinct. 

 The former is hyaline, the latter granular. The protoplasm has a 

 greenish or yellowish color. The nucleus is small, not very distinct. 

 There are numerous vacuoles. In the intestinal evacuations of 

 dysentery its protoplasm commonly contains many red blood- 

 corpuscles, upon which the organism seems to feed. 



Staining. — ^When stained with polychrome methylene-blue the 

 ectoplasm stains more deeply than the endoplasm. The nucleus 

 contains relatively little chromatin. 



Reproduction. — Multiplication takes place by binary division 

 after karyokinesis and by encystment and sporulation. The sporula- 

 * "Arbeiten a. d. k. k. Gesundheitsamt.," 1903, xrx, S47. 



