ANAEROBES IN INFECTED WOUNDS 441 



damaged or necrosed tissues, and infection by various anaerobes 

 of intestinal origin, though there are also some aerobes present 

 from the same and other sources. At an early stage the 

 number and variety of organisms, many of them spore-bearing, 

 form a very striking feature. As reactive processes, exudation, 

 leucocyte, emigration, etc., come into play, we find in favourable 

 cases that the anaerobes gradually diminish, while the aerobes 

 continue to flourish, though in deep clefts and in necrosed 

 tissue the former may persist for a long time. This change in 

 the flora becomes more marked as suppuration becomes estab- 

 lished and progresses ; the ordinary pyococci, apparently derived 

 from the skin, appear and multiply at the expense of the various 

 bacilli, enterococci, etc., till ultimately they are practically the 

 only organisms present. So far as serious complications are 

 concerned, we may say that in the early stages these are chiefly 

 due to the anaerobes and in the later stages to streptococci and, 

 to a less degree, to staphylococci. We have here to deal with 

 the anaerobes, and these have the following effects : (a) poison- 

 ing by toxins, the outstanding example being of course the 

 b. tetani ; (b) invasion of the tissues, the production of spreading 

 oedema, necrosis, and gaseous emphysema — generally comprised 

 under the term " gas gangrene " ; and (c) merely local inflam- 

 matory and putrefactive changes. The b. tetani has already 

 been treated of, and it has been shown that it has no more 

 infective or invasive properties than other saprophytic anaerobes. 

 The number of anaerobes separated from war wounds is large, 

 and with regard to them two general statements may be made. 

 In the first place, only a few have been shown to cause by 

 themselves definite spreading infections. Of these it is generally 

 accepted that the b. welchii is by far the most important, next 

 comes the vibrion septique, and then probably the b. oedematiens. 

 In the second place, the organisms which sometimes cause these 

 serious results are commonly present in wounds from which no 

 complications arise. There must accordingly be favouring con- 

 ditions in certain cases which lead to these grave and often fatal 

 results. This of course holds with regard to bacterial infections 

 in general, but it is especially well exemplified in the lesions 

 in question. The b. welchii, for example, is commonly present 

 in putrid wounds — in the great majority of cases it leads to no 

 harm, yet in a certain small proportion it causes one of the most 

 rapidly fatal infections known. As possible determining influ- 

 ences, we might' mention the degree of the injury, the dose of 

 infection, possibly the virulence of the invading organism, and the 

 adjuvant effect of other organisms. In the case of gas gangrene 



