478 



PROTOZOA 



hystolytica Schaudinn, which corresponds with the form studied by 

 Councilman and Lafleur and by Jiirgens, and which is pathogenic, 

 producing the true amoebic dysentery. He says that the pathogenic 

 variety has a more definite ectoplasm than the non-pathogenic; further- 

 more, that its nucleus contains less chromatin, making it more difficult 

 to demonstrate, it has a more varied form and is always situated eccen- 

 trically. This variety increases by division into two and by budding, 

 while the non-pathogenic variety increases by a regular division into 

 eight daughter forms (schizogony). In unfavorable conditions both 

 varieties may produce cysts. 



Morphology. The size of the amoeba coli is given variously by dif- 

 ferent authors within the limits of 7^ to 50/*, more commonly 12 p. to 30//. 

 In a state of rest it assumes a spherical shape which appears discoid 

 under the microscope. It may generally be distinguished from the other 

 cellular elements found in the feces by its pale-greenish tint and by its 

 stronger refraction of light. The outline of the body ordinarily appears 

 as a thin, single, dark line. The two portions of the body, the inner, or 



Amoeba coli. a. Containing red blood cells (Romer). 6. Mode of division (Harris). 

 c. Cyst with eight nuclei (Grassi). 



entoplasm, which is more or less granular and of a darker color, and 

 the outer, or ectoplasm, which is homogeneous and of a lighter color, 

 cannot always be made out and are more evident in the motile than in 

 the resting amoeba. 



The entoplasm constitutes the greater portion of the body of the 

 amoeba. In the smaller forms it is finely granular, and may show no 

 other structure. In the larger forms it is more coarsely granular and 

 may contain, in varying numbers, bacteria, starch bodies, cell detritus, 

 and red and white blood cells, in various stages of digestion. One to 

 several vacuoles have been seen in the entoplasm, but only Dock has 

 spoken of their infrequent pulsation. 



The ectoplasm forms a hyaline zone of variable thickness about the 

 entoplasm. It has the appearance, under the microscope, of finely 

 ground glass of a distinctly pale-green color. It seems often to pass out 

 into short, irregular pseudopods. 



The nucleus of the amoeba is 2/Jt to IfJ. in diameter. It is a more 

 or less spherical vesicle-like body containing a dark, chromatin inner 



