History. 499 



Virchow, in 1847, had a more restricted conception of the nature 

 of tuberculosis. This was based upon a histological foundation and 

 recognized as tuberculous such lesions only as presented small, well 

 marked non-vascular nodules or groups of nodules, or cheesy masses that 

 were evidently the result of the degeneration of such nodules. Accord- 

 ing to this view, however, he excluded. several forms of diseases which 

 are undoubtedly tuberculous in character, viz., tuberculosis of the 

 lymphatic glands (scrofula), tuberculous caseous pneumonia and tu- 

 berculosis of animals. 



Of the various forms of tuberculosis in animals, so-called pearl 

 disease in cattle in particular long ago attracted general attention, and 

 the regulations concerning meat inspection in various countries con- 

 cerned themselves with this question in detail. In the beginning of the 

 eighteenth century pearl disease was generally supposed to be identical 

 with syphilis of man, and supposed to be the result of unnatural inter- 

 course of syphilitic persons with animals (Pranzosenkrankheit). As a 

 result of this view all cattle affected with pearl disease were excluded 

 from use as food. At the end of the same century, however, this view 

 of the nature of pearl disease was found to be incorrect. But the appre- 

 ciation of the true nature of the disease was the result of a very gradual 

 development of our knowledge. During the first half of the last century 

 some authors (Gurlt, Hering, Fuchs) regarded pulmonary tuberculosis 

 of cattle and pulmonary consumption of man as identical, and others 

 (Gerlach, Spinola, Leysering) placed pearl disease of the peritoneum 

 of cattle in the same group. On the other hand, Virchow disputed the 

 occurrence of tuberculosis in animals altogether. According to his view 

 which was subsequently shared by Roll, the morbid growths of the lungs 

 and serous membranes were in reality neoplasms, sarcomata, which might 

 be considered identical with lympho-sarcomata of man. 



The question assumed a new aspect when in the year 1865 Villemin 

 proved by means of experimental infection that tuberculosis was trans- 

 missible from man to animals, and from animal to animal respectively. 

 Morgagni had already 200 years ago believed in the infectiousness of 

 pulmonary consumption and Klencke produced in 1843 tuberculosis in 

 rabbits by the intravenous injection of tuberculous material. But in 

 spite of this the spontaneous development of the disease according to the 

 humoral pathological theory continued to be asserted. Villemin obtained 

 positive results in his experiments with tuberculous material from man 

 as well as with material from cattle affected with pearl disease, and thus 

 furnished proof of the infectiousness of' tuberculosis as well as the 

 identity of the disease in man and in animals. In recent years Villemin 's 

 experiments have been abundantly verified by numerous repetitions, and 

 at the same time the various modes of infection have been elucidated. 

 These latter experiments have shown not only that tuberculosis is trans- 

 missible by means of subcutaneous or intraperitoneal infection (Klebs, 

 Bollinger, Kitt), intraocular inoculation (Cohnheim & Salomonssen, 

 Baumgarten), as well as through inhalation (Tappeiner, Weichselbaum) 

 of. tuberculous material, but furthermore they have shown that other 

 foreign substances could not produce similar pathological processes 

 (Martin, Ponfick, Langerhans). Semmer observed that the injection 

 of milk and blood from a cow with advanced pulmonary pleural tuber- 

 culosis into the jugular vein of a pig produced a pronounced general 

 tuberculosis. Chauveau (1868) as well as Gerlach (1869) succeeded in 

 producing the disease by feeding tuberculous material from cattle. 

 Klebs produced pearl disease of "the peritoneum by means of intraperi- 



