CPR Ee aa Re ee 
7 as 8 \ e 
917 
variations in environment as the addition or subtraction of blood, blood 
serum, bile, certain types of bacteria, ete. 
In. view of the above observations it is perfectly evident that amoebe 
found in a healthy intestine, or even in one in the early stages of disease, 
would be very likely to have a grayish color, regardless of the pathogenicity 
of the rhizopods. 
Shape and motility—aAll amoebe assume a great variety of shapes 
when in motion but when at rest, or encysted, they are invariably spherical 
or slightly oval. The oval shape is well marked and fairly constant 
in cultures of our amoebe “V;” this rhizopod also has an unusually 
prominent nucleus. Motility varies greatly, even in cultures of pure 
species, and from our observations it seems to depend, at least partially, 
upon physical laws. It may be quite rapid, or very slow; continuous, 
or, more frequently, intermittent. An alternating protrusion and with- 
drawal of pseudopodia may continue to take place for some time, without 
any change in the position of the ameeba. This period of comparative 
rest may be followed by one of great activity, but more usually it precedes 
the resting or encysted stages. 
Although progression is usually associated with the protrusion of 
pseudopodia, quite active motility can at times be observed without such 
protrusion. This progression is accomplished by a protrusion of the whole 
side of the amceba, which is followed by the remainder of the parasite in 
what appears to be a kind of rolling process; this motion may be kept 
up by an individual for some time, to be followed later by the usual 
pseudopodial motility. On the other hand, the parasite may encyst, 
without again showing true pseudopodial formation. In this class of 
amoeba one is particularly apt to notice currents of the protoplasm which 
are usually of a vortical nature, formed within the parasite. 
The actual distance traveled by amcebe and the rate of locomotion 
may very closely be determined from cultures, by inoculating in the 
center of a plate containing the media, as was described in our first 
publication, and then watching the rate of spread toward the edges of 
the Petri dish. These measurements permit us positively to state that 
a great variation exists in the rate of locomotion. In cultures of some 
amoebee, the surface of the media will be traversed in from forty-eight 
to sixty hours, while in others, during three or more days only a small 
area will be covered before encystment of all the parasites takes place. 
To judge from these observations, if rate of locomotion be of value in 
determining species, then such determinations are not in harmony with 
the other characteristics which are given for the differential diagnosis of 
“EB. col” and “EH. histolytica.” 
The formation of pseudopodia is probably a common property of all 
amoebe, and the size, shape, number, etc., of these protrusions may vary 
between wide limits. 
In size they range from almost thread-like projections to large, oval 
