282 BACTERIA 



and an extract of this in glycerine he termed " tuberculin." 

 It was made as follows : A veal broth containing peptone 

 and glycerine was inoculated with a pure culture of the 

 bacillus and incubated at 38 C. for six or eight weeks. An 

 abundant growth with copious film formation appeared. 



FLASK USED IN THE PREPARATION OF TUBERCULIN 



The culture was then concentrated by evaporation over a 

 water-bath until reduced to about one-tenth of its volume. 



The announcements in 1890 and 1891 to the effect that a 

 " cure " had been discovered for consumption will be re- 

 membered. The hopes thus raised were unfortunately not 

 to be realised. Koch advocated injections of this tuberculin 

 in cases of skin tubercle (lupus) and consumptive cases. In 

 many of these benefit was apparently derived, but its gen- 

 eral application was not founded upon any substantial basis. 

 Dead tissue, full of bacilli, could not thus be got rid of; nor 

 could the career of the isolated bacilli distributed through 

 the body be thus checked. 



Tuberculin has, however, found a remarkable sphere of 

 usefulness in causing reaction in animals suffering from 

 tuberculosis. Indeed, tuberculin is the most valuable means 

 of diagnosis that we possess (MacFadyen). When injected 

 (dose, 30-40 centigrammes) it causes a rise of one and a half 

 to three degrees. The fever begins between the twelfth and 

 fifteenth hour after injection, and lasts several hours. The 

 duration and intensity of the reaction have no relation to 

 the number and gravity of the lesions, but the same dose 

 injected into healthy cattle causes no appreciable febrile 

 reaction. The tuberculous calf reacts just as well as the 



