CHAPTER XXVIII. 



TUBERCULOSIS. 



TUBERCULOSIS is a communicable disease of man and animals, charac- 

 terised by the formation of new growths associated with the presence 

 of the tubercle bacillus. Yon Bayle, in 1810, was the first to describe 

 little growths like millet seeds, which were considered to be character- 

 istic of consumption or phthisis. Laennec, in 1834, attached much 

 more importance to the existence of caseous matter and classified 

 miliary tubercle, crude tubercle, granular tubercle, and encysted 

 tubercle, as varieties of tuberculosis. Virchow would not accept 

 all these varieties as tubercular, and only regarded those conditions 

 associated with the presence of miliary tubercles as genuinely 

 tubercular. Laennec's so-called crude tubercle, for example, was 

 simply due to pneumonic caseation. Yillemin threw entirely fresh 

 light upon this controversy by proving that tuberculosis was a 

 communicable disease. Rabbits and guinea-pigs, inoculated with 

 tubercular sputum or caseous tubercle, developed miliary tubercle in 

 a few weeks. Sanderson confirmed these experiments, and pointed 

 out that foreign bodies would produce experimental tubercul<>-i- 

 in rabbits. Cohnheim also confirmed the experiments of Villemin, 

 and maintained that tuberculosis was a specific inoculable disease, 

 and, therefore, everything was .tubercular which, on inoculation, 

 produced tuberculosis. Koch, in 1882, announced the discovery of 

 the tubercle bacillus, and expressed the opinion that without the 

 tubercle bacillus there could be no tuberculosis. Tubercle was 

 defined as tissue containing the tubercle bacillus, whatever might 

 be the clinical manifestations of the case, or the microscopical and 

 naked- eye appearances of the diseased parts. 



A tubercle is a small growth about the size of a millet seed. In 

 the early stage it is circular, hard, grey in colour, and lu-tn>n- : but 

 when it undergoes necrosis and caseation it becomes soft and yellowish. 

 Tn the very early stage it consists of a little collection of round 



375 



