CHAPTER XVIII. 



BACILLUS OF TUBERCULOSIS (KOCH'S TUBERCLE 

 BACILLUS). 



IT was a common belief many years ago in some 

 countries (kingdom of Naples, 1782) that tuberculosis 

 was an infectious disease; but it is only within com- 

 paratively recent times that the infectiousness of tuber- 

 culosis has become an established fact in scientific 

 medicine. Villemin (1868) was the first to show ex- 

 perimentally that tuberculosis might be induced in 

 healthy animals and man by inoculations of tubercu- 

 lous material. Others attempted to microscopically 

 demonstrate the origin of the disease (Ziirn, Buhl, 

 Klebs, Toussaint, etc.); but these investigations, 

 though paving the way to the discovery, which it 

 remained for Robert Koch to make, proved to be un- 

 satisfactory and incomplete. The announcement of 

 the discovery of the tubercle bacillus was made by 

 Koch, in March, 1882, at a meeting of the Physiolog- 

 ical Society of Berlin. At the same time satisfactory 

 experimental evidence was presented as to its etiolog- 

 ical relation to tuberculosis in man and in susceptible 

 animals, and its principal biological characters were 

 given. An innumerable number of investigators now 

 followed Koch into this field, but their observations 

 served only to confirm his original discovery. 



