348 MICRO-ORGANISMS AND DISEASE [chaP. 



these bacilli can be artificially cultivated outside the animal 

 body, and with such cultures by inoculation typical and 

 general tuberculosis can be produced, the tubercles thus pro- 

 duced again containing the same tubercle bacilli ; in short 

 he conclusively established that these bacilli are the vera causa 

 of the disease tuberculosis. The whole problem concerning 

 one of the most widespread, fatal, and little understood 

 diseases of man and animals was by these researches at 

 once cleared up, and considering the difficulties in the solu- 

 tion of the problem and the necessity of having had to 

 invent special methods by which this research was carried 

 to a successful issue, I have no hesitation in saying that 

 this discovery of Koch marks one of the most important, if 

 not the most important, landmark in pathology. Many are 

 the workers who since Koch have contributed towards fur- 

 thering details as to this question, but without any intention 

 of minimising the importance of any and every contribution 

 of facts towards a clear understanding of disease and its pre- 

 vention, I am, I think, within the limits of absolute correct- 

 ness in saying that Koch's publications on tuberculosis 

 {Deutsche med. Woch., 1881 ; and Mitth. aus d. K. Gesund- 

 heitsamte, ii.) contain almost the complete solution of the 

 problem. The best method, and always iised with success, 

 is the staining of film-specimens or of sections with Ziehl's 

 carbol fuchsin from twenty to thirty minutes at 35° to 40° C, 

 then wash in water for a second or two, then for a few 

 seconds (five to ten) in 30-33 per cent, nitric acid, wash 

 again in water and place in methyl-blue aniline oil for five 

 to ten minutes, wash and treat in the usual way, according to 

 whether cover-glass specimen or section. I have never seen 

 failure with this method : the tubercle bacilli are always 

 brought out with striking clearness. 



A great many modifications for staining the tubercle 



