36 CLINICAL BACTERIOLOGY. 



prominence or recession of the latter justifies the division 

 into infectious and toxic infections. 



The term infection indicates, in verbal expression, the 

 entrance of microorganisms into the animal body. With 

 the mere entrance of the disease-germs into the body the 

 infection that is, the generation of the disease is, how- 

 ever, by no means completed. The bacteria taken up may 

 again leave the body : may, for instance, pass through the 

 entire digestive tract without causing the slightest injury. 

 Thus, cholera-bacilli may temporarily be found in the in- 

 testinal evacuations of healthy individuals, and tetanus- 

 bacilli may be demonstrable in the intestinal contents of 

 healthy animals. The germs taken up may, however, 

 remain latent at the same place at which they later induce 

 disease, without doing this in the first instance. Thus, 

 bacteria, and especially those that we shall further on learn 

 to be the cause of inflammation and suppuration, are present 

 normally not only upon the entire cutaneous surface, but 

 also in the mouth, in the upper air-passages, in the entire 

 digestive tract, in the lower portion of the genito-urinary 

 apparatus, in the external ear, in the eye in short, where - 

 ever the external air has unobstructed access. The unin- 

 jured skin, however, as well as the normal mucous mem- 

 brane, does not permit the bacteria to force their way beneath 

 the surface ; and if they should multiply upon the surface 

 and generate poisons as, for instance, putrefactive bacteria 

 certainly do in the intestine these poisons, in the presence 

 of a normal mucous membrane, are either not at all ab- 

 sorbed or not as such. A lesion of the skin or of the mucous 

 membrane is first necessary to permit the entrance of the bac- 

 teria into the actual interior of the body (which normally is 

 free from germs) and, thereby, the development of infection. 

 Nor is the entrance of bacteria into the interior of the body 

 by any means synonymous with infection. Even if a lesion 

 has been induced, and if bacteria have gained entrance into 

 the tissues of the body, the disease may not be developed. 

 The bacteria may be taken up by cells of the body and be 

 destroyed (phagocytosis) ; or they may succumb to the 

 bactericidal property often possessed by the blood and the 

 fluids of the tissues. They may, further, remain free and, 

 in a certain degree, inactive until they die ; or, possibly, 

 induce the disease at a later period. Thus, as has been 

 demonstrated by an accidental observation of Vaillard, 



