CONGRESS ON TUBERCULOSIS. 
445 
Of course, I presuppose that we understand by tuberculosis only 
those morbid conditions which are caused by the tubercle-ba¬ 
cillus. 
In by far the majority of cases of tuberculosis the disease 
has its seat in the lungs, and has also begun there. From this 
fact it is justly concluded that the germs of the disease, i. e., 
the tubercle-bacilli, must have got into the lungs by inhalation. 
As to the question where the inhaled tubercle-bacilli have come 
from, there is also no doubt. On the contrary, we know with 
certainty that they get into the air with the sputum of con¬ 
sumptive patients. This sputum, especially in advanced stages 
of the disease, almost always contains tubercle-bacilli, some¬ 
times in incredible quantities. By coughing, and even speak¬ 
ing, it is flung into the air in little drops, i. e ., iu a moist condi¬ 
tion, and can at once infect persons who happen to be near the 
coughers. But then it may also be pulverized when dried, in 
the linen or on the floor, for instance, and get into the air in the 
form of dust. 
In this manner a complete circle, a so-called circulus vitio - 
sus, has been formed for the process of Infection, from the dis¬ 
eased lung, which produces phlegm and pus containing tubercle- 
bacilli, to the formation of moist and dry particles (which, in 
virtue of their smallness, can keep floating a good while in the 
air), and finally to new Infection, if particles penetrate with the 
air into a healthy lung and originate the disease anew. But the 
tubercle-bacilli may get to other organs of the body in the 
same way, and thus originate other forms of tuberculosis. This, 
however, is a considerably rarer case. The sputum of con¬ 
sumptive people, then, is to be regarded as the main source of 
the Infection of tuberculosis. On this point, I suppose, all are 
agreed. The question now arises whether there are not other 
sources, too, copious enough to demand consideration in the 
combating of tnberculosis. 
Great importance used to be attached to the hereditary 
transmission of tuberculosis. Now, however, it has been demon¬ 
strated by thorough investigation that, though hereditary tuber¬ 
culosis is not absolutely non-existent, it is nevertheless ex¬ 
tremely rare, and we are at liberty, in considering our practical 
measures, to leave this form of origination entirely out of ac¬ 
count. 
But another possibility of tubercular infection exists, as is 
generally assumed, in the transmission of the germs of the 
disease from tubercular animals to man. This manner of in- 
