340 TEXT-BOOK OF BACTERIOLOGY. 



their destructive action. The quantity of rods will, therefore, by- 

 no means always correspond to the severitj'^ of the disease, and the 

 practical hint conveyed by this statement is obvious. 



The bacilli appear within the vessels only exceptionally; they 

 are noticed in the blood only when the poisonous matter had en- 

 tered the circulatory system from the beginning. 



We know by the microscopic investigation, by cultivation out- 

 side of the animal, and by the successful transmission from artificial 

 cultures that the tubercle bacillus is the specific exciter of tuber- 

 culosis. How, then, can the peculiar manner and appearance of the 

 disease be explained bj' the living qualities of the original micro- 

 organism ? 



It will be interesting, above all, to ascertain the way by which 

 the bacillus finds, under ordinary conditions, entrance to the body. 

 All the doors of entrance at all possible have, in experiments, 

 proved accessible, and it was natuarlly supposed that these ways 

 were significant for natural infection, as with anthrax bacilli. 



Experience and clinical observation have vindicated this suppo- 

 sition. Infection occurs from the surface of the skin through wounds 

 by contusions, cuts, or otherwise. Thus the well-known corpse- 

 tubercles of the pathologists are small, well-circumscribed, locallj'- 

 limited settlements of tubercle bacilli surely established, as Kai'g 

 and others have found. Thus infections have occurred on the fin- 

 gers of people who had been injured by glass vessels and other 

 objects soiled by phthisical sputum. Some cases of tuberculosis 

 have become particularly famous which have been observed several 

 times in connection with the ritual circumcision of Jews. The 

 wound made by circumcision is closed and sucked by the operator's 

 mouth for the purpose of hsemostasis. If this is done (as has hap- 

 pened sometimes) by a man afflicted with phthisis, tubercle bacilli 

 may get into the' lesion, healing is delayed, the neighboring lym- 

 phatic glands swell, and finally a general tuberculosis of the chil- 

 dren is developed. 



Lupus is a tubercular affection of a peculiar character confined 

 to the skin. It is in its clinical symptoms but little similar to 

 other tubercular changes, and impresses one as a peculiar, unique 

 disease. Expert investigations have proved that it is uncondition- 

 ally a tubercular affection; and Koch especially succeeded not only 

 in proving the existence of bacilli in the lupus nodules, but also in 

 obtaining from them pure cultures of the bacilli. It cannot as yet 

 be definitely stated what the causes are for these differences in the 

 clinical attitude of ordinary pulmonary tuberculosis and lupus. 



We know that animals — for instance, rabbits — ma j' be infected by 



