Group V. 

 CHRONIC INFECTIOUS DISEASES. 



1. Tuberculosis. 



{Tuhcrcidose [German and Frcncli]; Tuhefcolosi [Italian].) 



Tuberculosis is a clironic contagious infectious disease of 

 man and domestic animals. It is caused by Koch's Bacillus 

 tu])erculosis or one of its varieties. Anatomically it is char- 

 acterized, in its incipient stage at least, by small iion-vascular 

 nodules known as tubercles which have a "tendency to undergo 

 cheesy degeneration. 



(a.) Tuberculosis of Mammals. 



{Pearl disease, Grapes; Perlsucht, Skrofidose, Liinf/enschwind- 



siicht, Stiersucht, Monatreiterei, Driisenkrankheit, Franz- 



osenkranklieit [German]; Cacheaia houm tuhercidosa, 



Phthisis pulmonum [Latin]; Pommeliere [French]; 



Malattia glandolare [Italian]). 



History. Tuberculosis, and particularly that form known as pul- 

 monary consumption, has from the remotest time been known as the 

 most prevalent disease of man. A large percentage of all deaths is due 

 to tuherculosis. The study of its nature had, therefore, until the be- 

 ginning of the last century, been contined almost exclusively to man. 

 Until recently, however, the results of these investigations amounted to 

 little more than theories or hypotheses. The peculiar character of the 

 tubercle was necessarily recognized by pathologists in the early history 

 of the study of the disease. Morton, as early as 1689, regarded the tu- 

 bercle as the anatomical foundation of pulmonary consumption. At a 

 later date special stress was laid upon the importance of cheesy degenera- 

 tion as characteristic of tuberculous lesions. While Bayle, in 1819, re- 

 stricted the definition of the tubercle to non-caseating, gray and trans- 

 lucent nodules, he as well as Baillie (1794) and Laennec (1819) con- 

 sidered pulmonary consumption and scrofula as identical morbid pro- 

 cesses. Laennec held the view that the tubercle owed its origin to a 

 specific tubercle-producing substance, soft and homogenous in con- 

 sistency, which was secreted from the blood, and that the inoculation of 

 this primary tubercle substance could produce the local development of 

 tuberculous tissue. As he, however, like later on Magendie and Roki- 

 tansky, attached undue importance to the cheesy character of tlie tu- 

 bercle, he included many other morbid processes which consisted of 

 simple degenerations. 



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