280 Dr. Edward E. Klein [Feb. 20, 



pneumonia. Not until Klencke and Villemin had shown by direct 

 experiment on animals that tuberculosis is inoculable was it grouped 

 amongst the infectious diseases. Since these experiments were first 

 published a large amount of work has been done, proving conclusively 

 that tuberculous material — that is, portions of the organs containing 

 the tubercular deposits (e. g. lung, lymph gland, spleen, &c.) — by 

 inoculation, by feeding, or by introducing it into the respiratory 

 tract, can set up typical tuberculosis in the experimental animals ; 

 the tubercular deposits in these exj^erimental animals again are 

 endowed with the power to propagate the disease in other animals. 

 Further, it was shown that the disease in cattle called " Perlsucht'* 

 was in all respects comparable to tuberculosis in man, and it is 

 accordingly now always called tuberculosis. 



A further, and perhaps the greatest, step was then made by Koch's 

 discovery in 1882 of the tubercle bacillus, and his furnishing the 

 absolute proof of its being the true cause of the disease. The 

 demonstration and identification of this microbe is now practised, I 

 might almost say, by every tyro, and it is of immense help to 

 diagnosis. In former years, and before 1882, the diagnosis of tuber- 

 culosis was not by any means an easy matter in many cases of chronic 

 lung disease ; since that year every physician in such cases examines 

 the expectoration of the patient, and the demonstration of the tubercle 

 bacilli makes the diagnosis of tuberculosis absolutely certain. Not 

 only in medical, but also in many surgical cases, e. g. certain forms 

 of chronic disease of bones and joints, particularly in children, the 

 demonstration of the tubercle bacilli is of essential importance, and 

 by these means diseases like lupus of the skin, scrofula, and certain 

 diseases of bones and joints not previously known as tuberculosis, 

 are now proved to be so. The same applies to animals ; wherever in 

 a diseased organ of man or animal the tubercle bacilli can be demon- 

 strated, the disease must be pronounced as tuberculosis. 



The proof that the tubercle bacillus is the actual cause of the 

 tubercular disease was established by Koch beyond possibility of 

 doubt. Cultures in artificial media were made from a particle of a 

 tubercular tissue, either of a human being or of cattle afi'ected with 

 tuberculosis, or of an experimental animal tubercular by ingestion, 

 or by injection with tuberculous matter, and in all cases crops of the 

 tubercle bacilli were obtained. Such cultures were then carried on 

 from subculture to subculture, through many generations, outside the 

 animal body ; with a mere trace of any of these subcultures, however 

 far removed from the original source, susceptible animals were 

 infected, and all without fail developed tuberculosis, with the tubercle 

 bacilli in the morbid deposits of their organs. The discovery of the 

 tubercle bacilli and the demonstration that they are constantly pre- 

 sent in the tubercular deposits of the typical tuberculosis, and the 

 proof by experiment on living animals that they are the actual cause 

 of the disease, are not all that we have learned, for it has also been 

 shown that certain diseases, like the dreaded and disfiguring disease 



