The Avenues of Infection 67 



AVENUES OF INFECTION. 



The skin seems to form an effectual barrier against the 

 entrance of bacteria into the deeper tissues. A few higher 

 fungi Trycophyton, Microsporon, Achorion, etc. seem 

 able to establish themselves in the superficial layers of the 

 cells, invade the hair-follicles, and so reach the deeper 

 layers, where morbid changes are produced. The minute 

 size of the bacteria makes it possible for them to enter 

 through lesions too small to be noticed. Garre applied a 

 pure culture of Staphylococcus pyogenes aureus to the skin 

 of his forearm, and found that furuncles developed in four 

 days, though the skin was supposed to be uninjured. Bock- 

 hart moistened his skin with a suspension of the same organ- 

 ism, gently scratched it with his finger-nail, and suffered 

 from a furuncle some days later. 



The greater number of surgical infections result from the 

 entrance of bacteria through lesions of the skin. It makes 

 but little difference to what depth the lesion extends, 

 abrasions, punctures, lacerations, incisions, the protective 

 covering is gone and the infecting organisms find themselves 

 in the tissues, surrounded by the tissue lymph, under con- 

 ditions appropriate for growth and multiplication, provided 

 no inhibiting or destructive mechanism be called into action. 



The digestive apparatus is the portal through which 

 many infections take place. The Bacillus diphtheriae, 

 finding its way to the pharynx, speedily establishes itself 

 upon the surface, producing pseudomembranous inflam- 

 mation there. Typhoid bacilli, dysentery bacilli, cholera 

 spirilla and related organisms, finding their way to the 

 intestine, where the vital conditions are appropriate, take 

 up temporary residence there, to the inconvenience of the 

 host, who suffers from the respective infections. 



Various organisms pass from the pharynx to the tonsils 

 and so to the lymph-nodes and deeper tissues of the neck, 

 where their first operations may be observed. 



It is supposed by some pathologists that the digestive 

 tract is a constant menace to health in that it regularly 

 admits bacteria, through the lacteals, and perhaps through 

 its capillaries, to the blood, where under slightly abnormal 

 conditions they might do harm. According to Adami,* 



* "Jour, of the American Medical Association," Dec. 16 and 23, 

 1899, vol. xxxm, Nov. 25 and 26. 



