TEXT-BOOK OF BACTERIOLOGY. 227 



eluding- sentence of his communication was : " We can with good 

 reason say that the tubercle bacillus is not simply one cause of 

 tuberculosis, but its sole cause, and that without tubercle bacilli you 

 would have no tuberculosis." 



Through the microscopical recognition of tubercle bacilli in all 

 properly-examined cases of tuberculosis, and only in them, and 

 through successful cultivations of the germs outside the body and 

 their successful transmission and reproduction of the disease, he 

 proved his assertions, and in .this way established a wonderful ad- 

 vance in medical knowledge. 



Now, there was no doubt as to what was to be considered tuber- 

 culosis and what was not. " In those processes where you find 

 tubercle bacilli, there is true tuberculosis," no matter what the 

 macroscopical or microscopical pathological picture is, or what the 

 clinical evidence may show in single cases. The subsequent advan- 

 tages from a diagnostic point of view are evident. 



Wherever processes of a tubercular nature have occurred the 

 bacilli have been the factors, and therefore they are observed in 

 tubercular tissue and in the excretions of tubercular persons, es- 

 pecially in the sputum of such individuals. 



They are very slender, medium-sized rods, somewhat smaller 

 than a human red blood-corpuscle. They have clearly-rounded 

 ends and are seldom perfectly straight, more often bent like a 

 fiddle-bow. Usually they are seen single, less often two together, 

 and here and there are to be seen larger chains of five to six mem- 

 bers. They are incapable of voluntary motion. 



The question whether the tubercle bacilli form spores has as 

 yet not been positively decided. In the examination by the hanging 

 drop, we do not see in the interior of the rods those sharply-cir- 

 cumscribed glistening bodies of definite shape which are recognized 

 as characteristic of sporulation of bacteria. If we stain the prepa- 

 rations, we observe very frequently in the interior of the bacilli 

 small bright spaces, often in regular arrangement, reminding one 

 of spores. In fact, they are often called such. 



Still, one observes by closer examination facts which will not 

 wholly agree with the theory of sporulation. At one time we will 

 not infrequently find in the same rod several of these structures, 

 which in all other instances known up to the present time only 

 produce a single spore. 



Further, the outlines are usually not sharp, the boundary be- 

 tween the clear and the stained portion is somewhat obscured, the 

 size of the clear spaces varies, and lastty, their form also differs from 

 those of the usual spore because as a rule they do not appear round 



