CHAPTER X. 



TUBERCULOSIS. 



The cause of tubercle was proved by Koch in 1882 to be the 

 organism now universally known as the tubercle bacillus. Prob- 

 ably no other single discovery has had a more important effect 

 on medical science and pathology than this. It has not only 

 shown what is the real cause of the disease, but has also sup- 

 plied infallible methods for determining what are tubercular 

 lesions and what are not, and has also given the means of study- 

 ing the modes and paths of infection. 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 produced' 

 tuberculosis in rabbits by intravenous injection of tubercular materia], but he 

 only concluded from these experiments that the cells of tubercles could multi- 

 ply 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 inves- 

 tigate the infectious character of tubercle by systematic experiments, and to- 

 demonstrate the regularity with which tuberculosis can be transmitted by in- 

 oculation with tubercular material. His first observations were published in 

 1865. He produced tuberculosis in animals not only by tubercular material 

 fi-om the human subject, but also by portions of what were known as the Perl- 

 sucht 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, how- 

 ever, aroused a storm of opposition from all sides. The opposition was at 

 first chiefly on theoretical grounds, but later also from experimental results. 

 Investigators who repeated Villemin's experiments obtained similar results so 

 far as the production of tuberculosis by tubercular material was concerned, 

 but many found that tuberculosis also followed inoculation with non-tubercular 

 material (such as pus from pyaemic abscesses, portions of decomposed tissue,, 

 etc.), and even by the mere introduction of setons. The general opinion 

 came to be strongly against the existence in tubercle of an infective agent 

 of specific nature, and along with this there prevailed great confusion as to- 

 the distinction between tubercular and non-tubercular lesions. 



By the work of Armanni and of Cohnheim and Salomonsen (1870-80) it 

 had been demonstrated that tubercle was an infective disease. The latter 



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