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XXXIV] days later, that the habitat of the parasite is not so much the pus occupying the general abscess cavity as that immediately in contact with the wall and the breaking-down tissues themselves. This is an inference entirely in harmony with Councilman and Lafleur's demonstration, confirmed by Marshall, of the parasite in the still living tissues around the abscess. In my experience the presence of the amœba does not affect prognosis unfavourably. Lafleur says it does: I cannot agree with him. In common with many other observers I have often seen amœbic liver abscess recover completely and rapidly after operation. Other protozoa have been found in liver pus. Thus, both Grimm and Berndt have found numerous active flagella-like organisms therein. Some time ago, in the expectorated pus from a liver abscess discharging through the right lung, I found a ciliated infusorian resembling Balantidium coli. In the pus of a large proportion of liver abscesses both microscopical examination and culture may fail to detect the usual pyogenic micro-organisms. To harmonize this well-established fact with modern views on the cause and nature of the suppurative process, it has been suggested that, though in these sterile abscesses micro-organisms had originally been present, they had subsequently died out. This view receives a measure of support from the fact that in a proportion of instances there is no difficulty in demonstrating in the pus the ordinary pyogenic bacteria and, sometimes, the Bacterium coli commune. It by no means follows from this circumstance, however, that bacteria are a necessary factor in the production of all liver abscesses.

Encystment.— In rare instances the pus of liver abscess, instead of possessing the chocolate colour and viscid consistency described above, is yellow and creamy. This is particularly the case when the abscess becomes encysted— an occasional event. The walls of these encysted abscesses are thick, smooth, resistant, and fibrous. In time their contents become cheesy, and ultimately cretified; in the latter event the cyst shrivels up and contracts to a small size.