The Avenues of Infection 67 



found that carbon particles readily passed through the 

 intestinal mucosa, entered the lymphatics and were so 

 thrown into the venous circulation and so carried to the 

 lung, this being the common method by which anthracosis 

 was produced. 



There are enough of these experiments to make it probable 

 that the wall of the intestine is permeable to bacteria, and 

 that in small numbers they constantly enter the blood of 

 healthy animals, to be disposed of by mechanisms yet to be 

 described. 



Many of the bacteria penetrating the intestine must be 

 retained in the lymph nodes; others, as in the experiment 

 with the tubercle bacilli, meet destruction before they reach 

 the blood; the remainder must reach the blood alive. 



The presence of colon bacilli in the greater number of the 

 organs shortly after death has led some pathologists to 

 assume that they readily pass through the intestinal walls 

 during the death agony, but although experiments have been 

 made to prove and to disprove it, the matter is still con- 

 troversial. Undoubtedly in the final dissolution some 

 change takes place in the constitution of the individual by 

 which general invasion by bacteria is made more easy than 

 under normal conditions. 



The respiratory apparatus affords admission to a few 

 micro-organisms whose activities seem more easily carried 

 on there than elsewhere. Although it is still controversial 

 whether the inhalation of tubercle bacilli is as frequent a 

 mode of conveying that organism into the body as was once 

 supposed, it cannot be denied that its inhalation will account 

 for the far greater frequency with which tuberculosis affects 

 the lungs than other organs of the body. 



Pneumonia, caused in an immense majority of cases by 

 the pneumococcus of Fraenkel and Weichselbaum, probably 

 results from the entrance of the organism into the respira- 

 tory tissues directly. 



The entrance of the unknown infectious agents causing 

 measles, German measles, smallpox, and scarlatina, can best 

 be accounted for by supposing that they are inhaled into 

 the lungs and thus enter the blood. 



The genital apparatus is the portal of entry of micro- 

 organisms whose early or chief operations are local. Among 

 these are the gonococcus, which causes urethritis, vaginitis, 

 balanitis, posthitis, endometritis, orchitis, salpingitis, vesicu- 



