ENTRANCE AND SPREAD OF. BACTERIA 221 



healthy serum or cells of the body, and no harm results. 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 inflammatory and suppurative conditions met with 

 clinically. In some cases of multiple suppurations due to staphy- 

 lococcus infection, only an apparently unimportant surface lesion 

 is present ; whilst in others no lesion can be found to explain 



FIG. 56. Minute focus of commencing suppuration in brain case 

 of acute ulcerative endocarditis. In the centre a small haemorrhage ; 

 to right side dark masses of staphylococci ; zone of leucocytes at 

 periphery. 



Alum carmine and Gram's method, x 50. 



the origin of the infection. The term cryptogenetic 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 sum- 

 marised 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 



