yS Infection 



various methods, no carbon particles seemed to be transported from 

 the alimentary to the puhnonary tissues. 



But there are enough experiments recorded 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 controversial. Undoubtedly in the final dis- 

 solution some change takes place in the constitution of the individual 

 by which general invasion by bacteria is made more easy than under 

 lormal conditions. 



The respiratory apparatus affords admission to a few micro-organ- 

 isms whose activities seem more easily carried on there than else- 

 where. 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 pneu- 

 mococcus of Fraenkel and Weichselbaum, probably results from the 

 entrance of the organism into the respiratory 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, vesiculitis, cystitis, oophoritis, 

 sometimes peritonitis, and rarely endocarditis; the bacillus of 

 Ducrey, that causes the chancroid or soft sore; and the treponema of 

 syphilis. In more rare cases other organisms, such as the common 

 cocci of suppuration and the tubercle bacillus, may also be trans- 

 mitted from individual to individual by sexual contact. 



The placenta usually forms a barrier through which infectious 

 agents find their way with difficulty. A study of this subject by 

 Neelow* shows that the non-pathogenic organisms do not pass 

 from the mother through the placenta to the fetus. Some patho- 

 genic micro-organisms, however, readily pass through, and a few 

 'Centralbl. f. Bakt.," etc., Aug., 1902, I. Abt., Bd. xxxi, Orig., p. 691. 



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