INTESTINAL AMEB^ 141 



nor any country, has yet been discovered in which infections with 

 this species are not common." 



There is no effective treatment for E. coli infections. Since 

 the parasites do not live in the tissues they are, like the intestinal 

 flagellates, unaffected by emetin. 



Councilmania lafleuri (Fig. 41), formerly confused with En- 

 damoeba coli, has recently been described by Kofoid and Swezy. 

 The free amebse are very active, and creep about with re- 

 markable rapidity. They commonly produce only a single pseu- 

 dopodium at a time, and this is composed entirely of clear 

 ectoplasm. The pseudopodia are peculiar in that they are shot 

 out almost instantaneously for the greater part of their length. 

 The endoplasm is usually loaded with food vacuoles containing 

 bacteria, faecal particles, and also frequently red blood corpuscles, 

 the latter fact indicating that this parasite, like Endamceba 

 histolytica, is in part a tissue parasite. The most striking and 

 distinctive characteristic is the method of escape of amebulse 

 from the cysts by a repeated process of budding, a single nucleus 

 at a time slipping out through a pore in the cyst wall, surrounded 

 by a part of the cytoplasm (Fig. 41C). It is probably the only 

 parasitic ameba in which the cysts act as a means of multiplica- 

 tion without transfer to a new host. 



Another common intestinal ameba of man is Endolimax nana, 

 (Fig. 38), the principal characteristics of which are given under 

 the genus Endolimax on p. 129. It is a small ameba measuring 

 from 6 M to 12 /z (T^TF to -y^ f an mcn ) m diameter. It creeps 

 sluggishly like E. coli, and, like that species, often contains numer- 

 ous food vacuoles filled with bacteria. The four-nucleated cysts 

 (Fig. 38B) might be confused with those of E. histolytica, but are 

 distinguishable by their small size (usually 8 to 10 // by 7 to 8 ju), 

 their oval shape, and the peculiar structure of the nuclei, described 

 on p. 129. This is a very common human parasite, having been 

 found in as high as 33 per cent of some series of examinations 

 made by competent workers. Although frequently found in 

 dysenteric patients associated with Endamceba histolytica, there 

 is no evidence that this species is at all pathogenic. Like E. coli, 

 this ameba cannot be eliminated by emetin or any other drugs 

 although it temporarily disappears during emetin treatment. 

 Its exact habitat in the intestine is not known, but it is certainly 

 not a tissue parasite. 



