CHAPTER XVIII. 
BACILLUS OF TUBERCULOSIS (KOCH’S TUBERCLE 
BACILLUS). 
Ir 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, ete.); 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. 
