PEACTICE OF MEDICINE AND HYGIENE 



inherited weakness. It was met by apathy and 

 hopelessness. The whole modern view of this 

 disease, prompting mankind to overcome it 

 and stamp it out, has been made possible by 

 animal experimentation. . Tuberculosis is so 

 common in the lower animals that its scientific 

 study has been accompanied with little diffi- 

 culty since the discovery of the causative fac- 

 tor, the tubercle bacillus, by Koch in 1881. 

 The way for Koch's discovery was paved by 

 the work of Klencke and Villemin, who experi- 

 mented upon animals with infectious materials 

 and proved its infectious nature. Since that 

 time an entirely new light has been thrown 

 upon the disease. The identification of this 

 bacillus marked the beginning of its conquest. 

 By virtue of Koch's discovery, the danger of 

 tuberculosis from the dust of dried sputum is 

 demonstrable, and the positive diagnosis of 

 tuberculosis is made possible. The infecting 

 power of flies which alight upon tubercu- 

 lous expectorations is proved. By no other 

 means could the tuberculous conductor who 

 moistened his finger with his saliva have 

 been convicted of handing out an infected 

 transfer. 



The disease is found in all of the domestic 

 6 67 



