It has long been known that acute infectious diseases may be accompanied by edema of the skin and subcutaneous tissues. While in some cases of pneumonia this edema may be sufficiently well marked to cause pitting on pressure, in the majority of cases, such evidence is not present, notwithstanding definite water retention. It would be expected, following the explanation of Fischer,1 that edema would be an almost constant accompaniment of pneumonia, for we have here a disease in which several factors,2 as the increase in ammonia output, the decreased carbon dioxid content of the blood, etc., make it very probable that there is an interference with oxidative processes of the organism.
According to Fischer the inhibition of oxidation, with the concomitant increase in acidity, is of great importance in the production of edema. That this edema may occur and not be appreciated is not