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animal, but if this last direct inoculation from animal to animal is 
continued, the bacteria are gradually eliminated, and finally bacteria- 
free amoebic liver abscesses result. However, by using this procedure 
the percentage of infection is again somewhat decreased, until in every 
series of animals in which we have tried it, infection will finally no longer 
occur. This failure to infect is difficult to explain, but as it also occurs 
in other experiments which produce strict parasitism, we are inclined 
to look on it as an expression of the errant réle which absolute parasitism 
forces upon these protozoa. 
On the other hand, if the symbiotic organism is one like B. typhosus, 
capable of producing bacteriemia in monkeys, and if, from twenty-four 
to forty-eight hours before the liver inoculations, the animal is injected 
subcutaneously or intraperitoneally with a pure culture of B. typhosus, 
then a maximum percentage of abscesses is produced and the infection 
can be kept active from animal to animal, no matter whether the infecting 
material be taken from subcultures or be transferred by direct inoculation 
of the pus from one abscess into the liver of the next monkey. In these 
cases secondary abscesses are also sometimes found in the lungs and occa- 
sionally in the spleens of the animals inoculated. 
It is more difficult to produce an intestinal infection with subcultures 
from abscesses produced by any of the above methods than it is with 
ameoebse which are grown from saprophytic sources or from the intestine. 
The reasons for this—at first sight rather astonishing—observation are 
obvious from what has gone before, for although the parasitic character 
of the amoeba has been raised, its selectiveness has also increased to a 
point where it rarely finds a satisfactory symbiosis in the saprophytic 
flora of the intestine. It is now easy to understand why the older workers 
had so much more difficulty in infecting animal intestines with the 
contents of amoebic liver abscesses than they had with the amcebe from 
the dysenteric intestine. 
INTRAPERITONEAL INFECTION, 
Infection by the injection of cultures of amoebe into the peritoneal 
cavity is more difficult than it is by inoculation into the liver, and it is 
rarely accomplished without some preliminary treatment of the cultures 
and of the animals. However, with proper care, a most extensive amoebic 
infection of the omentum and other abdominal structures may be ob- 
tained in monkeys and in guinea pigs. 
(1) If cultures of amcebe from various extraneous sources or even 
from the bowel are injected directly into the peritoneal cavities of healthy 
monkeys, infection almost never occurs, and this is true regardless of the 
symbiotic bacteria present, but— 
(a) If, for example, a culture of amoebe and B. typhosus, which has 
failed to infect hy inoculation in the abdominal cavity, is first inoculated 
into the liver, and subcultures are then made from the abscess, these sub- 
aT see 
