CHAPTER IX. 



TUBERCULOSIS. 



THE cause of tubercle was proved by Koch in 1882 to be 

 the organism now universally known as the tubercle bacillus. 

 Probably no other single discovery has had a more im- 

 portant effect on medical science and pathology than this. 

 It has not only shown what is the real cause of the disease, 

 but has also supplied infallible methods for determining 

 what are tubercular lesions and what are not, and has also 

 given the means of studying the modes and paths of in- 

 fection. A definite answer has in this way been supplied 

 to many questions which were previously the subject of 

 endless discussion. 



Historical. Klencke in 1843 made the statement that he had pro- 

 duced tuberculosis in rabbits by intravenous injection of tubercular 

 material, but he only concluded from these experiments that the cells 

 of tubercles could multiply and reproduce the disease, and he appears 

 to have placed little importance on the discovery. Villemin has the 

 honour of having been the first to investigate the infectious character 

 of tubercle by systematic experiments, and to demonstrate the 

 regularity with which tuberculosis can be transmitted by inoculation 

 with tubercular material. His first observations were published in 

 1865. He produced tuberculosis in animals not only by tubercular 

 material from the human subject, but also by portions of what were 

 known as the perlsucht nodules in cattle, and came to the conclusion 

 that perlsucht was due to the same virus as tubercle. He concluded 

 that this virus was comparable in its mode of action with that of other 

 infectious diseases. 



These views, however, aroused a storm of opposition from all sides. 

 The opposition was at first chiefly on theoretical grounds, but later 



