XIV. 
PATHOGENIC AKROBIC BACILLI NOT DESCRIBED IN 
PREVIOUS SECTIONS. 
A CONSIDERABLE number of saprophytic bacilli are pathogenic for 
small animals when injected into the circulation, or subcutaneously, 
or into a serous cavity in considerable quantity—one to five cubic 
centimetres or more—but fail to produce any appreciable effect 
when introduced into the bodies of these animals in minute doses, 
and do not multiply in the blood to any considerable extent, al- 
though in fatal cases they may usually be recovered in cultures from 
the blood and tissues. These bacilli are pathogenic by reason of the 
toxic ptomaines produced by them, or because of local inflammatory 
processes which they induce, or for both of these reasons combined. 
Some of them may also, under certain circumstances, multiply in 
the blood and thus give rise to septiceemia as well as to toxeemia ; 
this is the case, for example, with the “‘ colon bacillus” of Escher- 
ich. When injected in considerable quantity into the circulation 
of a guinea-pig it causes the death of the animal within twenty-four 
hours, and the bacillus is found in the blood in great numbers ; but 
minute amounts injected into a vein, or larger amounts injected 
subcutaneously, do not usually produce general infection. It is, 
therefore, not included among the ‘‘ bacilli which produce septi- 
ceemia in susceptible animals.” There is reason to believe, however, 
that under certain circumstances this bacillus may have sufficient 
pathogenic potency to produce a genuine septicemia in guinea-pigs. 
Thus the original cultures of Brieger’s bacillus, which appears to be 
a variety of the colon bacillus, are reported to have produced fatal 
septicemia in guinea-pigs when injected subcutaneousiy in small 
amounts. <A strict division into pathogenic bacilli which produce 
general blood infection—septicemia—and those which produce a 
fatal result owing to the production of toxic chemical substances is 
not possible; for many pathogenic bacteria produce general infection 
when injected in comparatively large doses, and at the same time 
give rise to symptoms of toxemia; or general infection may occur 
in animals of one species, and fatal toxsmia without septicemia in 
