116 
BACTERIOLOGY. 
had not been outside of the State of New York in 
several years. 
Two species of amebse are found in man, one is 
pathogenic, the Entamoeba hystolitica, the other is 
harmless, the Entamoeba coli. They exist in both a 
vegetative and encysted form. The vegetative form is 
not so infectious as the encysted form, the latter being 
much more resistant. 
In structure the ameba, in the vegetative form is 
composed of an outer clear zone and an inner granular 
zone of protoplasm which contains the nucleus. The 
protoplasm frequently contains cavities called vacuoles. 
It moves by extending a portion of the outer clear zone, 
called a pseudopod, into which the rest of the cell body 
flows. These pseudopods may also embrace small par¬ 
ticles of food and take them into the body of the cell. 
In the encysted stage the outer layer of protoplasm 
becomes dense and forms a cyst wall. There is no 
motility in this stage. 
Reproduction takes place either by simple division 
or by budding, in which a portion of the nucleus and 
the protoplasm protrude from the margin and are 
eventually pinched off to make a new cell. 
The infection with amebse comes chiefly from 
chronic carriers. Those having to do with the prep¬ 
aration of food are especially dangerous. It is in the 
encysted form that the ameba is most infectious. 
The ingested amebse lodge in the intestine and 
cause changes leading to ulceration. They frequently 
find their way into the liver to cause abscess formation. 
