Amebic Dysentery 691 



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 al- 

 kaline. It usually measures between 10 and 20 ^ in diameter 

 when free, but when encysted from 15 to 50 p. It is sphe- 

 roidal 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 methylene-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 organ- 

 ism first becoming 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 

 the intestine 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. When present it is usually in great numbers, so 

 that its discovery in the evacuations is usually easy. 



Morphology. It is usually considerably larger than Enta- 

 moeba coli and varies in diameter up to 50 /w. When at rest 

 it is spherical, when active it is very irregular. Its move- 

 ment 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. When examined in the in- 



