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No, 4.—Monkey (M. cynomolgus) inoculated in the abdominal cavity with an 
encysted culture of the original cabbage ameebe in pure symbiosis with B. typhosus. 
No. 5.—Monkey (M. cynomolgus) inoculated directly into the liver with the 
_ same culture as that used for No. 4. 
At autopsy, one week later, No. 4 was found to be normal and No. 5 showed 
a liver abscess from which ameebe and B. typhosus were obtained by culture. 
No. 6.—Monkey (M. cynomolgus) was inoculated in the abdominal cavity with 
an encysted culture from No. 5. 
No, 7.—Monkey (M. cynomolgus) was given, subcutaneously, 2 cubie centi- 
meters of a bouillon culture of B. typhosus and twenty-four hours later was 
inoculated in the abdominal cavity with the same culture as was used to 
inoculate No. 6. 
At autopsy, one week later, No. 6 was found to be normal with the exception 
of a small abscess in the abdominal wall, and No. 7 showed multiple abscesses 
in the omentum and liver, and one in the lung. These abscesses contained amcebie 
and bacteria, but only the B. typhosus grew on culture. 
No, 8.—Monkey (M. cynomolgus) inoculated in the abdominal cavity with the 
contents of an abscess occurring in the omentum of No. 7. 
No, 9.—Monkey (M. cynomolgus) which had eighteen hours previously received 
2 cubic centimeters of a bouillon culture of B. typhosus was inoculated in the 
same manner as No. 8. 
At autopsy, four days later, both these monkeys showed ameebie abscesses in 
the omentum, but the infection was much more extensive in No. 9. 
(b) Decreasing the virulence; avirulence——Another consideration in 
this connection which is second in importance only to that brought out 
by the power of amcebe to increase in virulence under proper environment, 
is the question of the loss of virulence by these protozoa. 
In discussing this portion of the pathological biology of these organ- 
isms, both the question of symbiosis and of direct virulence must be kept 
in mind, just as it is when the increase of virulence is considered. We 
have already shown the great difficulty, and often the impossibility, of 
causing amcebe to return to a condition at all like their former mixed 
environment, when once they have been grown on solid media in pure 
cultures of bacteria. This is even true when all the known facts concern- 
ing symbiosis are borne in mind and are used in attempts gradually to 
induce the parasites to return to their former mixed association. Pure, 
mixed cultures may occasionally be transferred from solid to liquid media 
in the same pure symbiosis, but attempts to introduce other organisms 
and thus to have mixed bacterial cultures usually result in the disap- 
pearance of the amcebe. 
Similar results are obtained when working with symbioses in the higher 
animal tissues. Although amoebe may be changed from symbiosis with 
one bacterium to that with another in cultures, after animal infection 
has been brought about, growth on artificial media is usually only possible 
with the organism which was present in the ameebic lesion in the animal. 
If the animal infection is continued for a sufficient length of time to 
allow symbiosis with the tissues or juices of the body to be established, then 
