1 82 SUPPURATION AND ALLIED CONDITIONS. 



from the latter being especially numerous. In most cases 

 they are killed by the action of the healthy serum or cells 

 of the body, and no harm results. (It is to be noted in 

 this connection that it has been proved experimentally that, 

 even in the case of a pathogenic organism, a considerable 

 number can be destroyed in the blood of a healthy animal.) 

 If, however, there be a local weakness, they may settle in 

 that part and produce suppuration, and from this other 

 parts of the body may be infected. Such a supposition as 

 this is necessary to explain many cases of suppuration met 

 with clinically. Thus the liability of diseased heart valves 

 to become infected by organisms and thence to assume an 

 ulcerative character, is well known. Conditions such as 

 suppurative periostitis and osteomyelitis, multiple suppura- 

 tive arthritis, suppurative inflammations of several serous 

 surfaces, and other similar conditions can be explained 

 only in the same way. In some cases of multiple suppura- 

 tions due to staphylococcus infection, which we have had 

 the opportunity to examine, only an apparently unimport- 

 ant surface lesion was present j whilst in others no lesion 

 could be found to explain the origin of the infection. The 

 organs or parts of the body affected vary much in different 

 cases, the distribution being explicable only by selective 

 action on the part of the organisms. In some cases the 

 lungs are especially affected, in others the kidneys, in 

 others the bones or joints, and so on (Figs. 51, 52). The 

 term cryptogenctic has been applied by some writers to such 

 cases in which the original point of infection cannot be 

 found, but its use is scarcely necessary. 



The paths of secondary infection may be conveniently 

 summarised thus : First, by lymphatics. In this way the 

 lymphatic glands may be infected, and also serous sacs in 

 relation to the organs where the primary lesion exists. 

 Second, by natural channels, such as the ureters and the 

 bile ducts, the spread being generally associated with an 

 inflammatory condition of the lining epithelium. In this 

 way the kidneys and liver respectively may be infected. 

 Third, by the blood-vessels : (a) by a few organisms gaining 



