86 BACTERIOLOGY FOR NURSES 



demonstrated by a simple watery solution of a basic 

 aniline dye, and it was only after prolonged staining for 

 twenty-tour hours, with a solution of methylene-blue 

 with caustic potash added, that he was able to reveal the 

 presence of the organism. Then, in the second place, 

 all attempts to cultivate it on the ordinary media failed, 

 and he only succeeded in obtaining growth on sohdified 

 blood-serum, the method of preparing which he himself 

 devised, inoculations being made on this medium from 

 the organs of animals artificially rendered tubercular. 

 The fact that growth did not appear till the tenth day at 

 the earliest, might easily have led to the hasty conclusion 

 that no growth took place. All difficulties were, however, 

 successfully overcome. He cultivated the organism by 

 the above method from a great variety of sources, and by 

 a large series of inoculation experiments on various ani- 

 mals, performed by different methods, he conclusively 

 proved that bacilli from these different sources produced 

 the same tubercular lesions and were really of the same 

 species. His work was the means of showing conclusively 

 that such conditions as lupus, "white swelHng" of joints, 

 scrofulous disease of glands, etc., are really tubercular in 

 nature." (Muir and Ritchie.) 



Koch's discovery is considered the most important 

 single discovery in the history of medical science. 



Tubercle bacilli are minute rods from 2 /i. to 3.5 /* 

 or 4 ju. in length and about 0.5 /a in breadth, occurring 

 singly or in small groups, and surrounded by a cap- 



