XL] BACILLUS : PATHOGENIC FORMS. 119 



artificially produced (by inoculation with human or bovine 

 tuberculous matter) in cats, guinea-pigs, rabbits, and rats, 

 and in spontaneous tuberculosis in birds (hens), Koch 1 

 found in the fresh state, and particularly after staining with 

 methylene-blue and vesuvin, peculiar fine bacilli, some with 

 bright oval spores, some without, some smooth and homogene- 

 ous-looking, others more of a beaded appearance. One cubic 

 centimetre of a concentrated alcoholic solution of methylene- 

 blue is mixed with 200 ccm. of distilled water ; to this are 

 added two ccm. of a ten per cent, solution of caustic potash. 

 In this solution the fresh or hardened sections or particles of 

 tubercles are kept for half an hour if heated up to 40 C., or 



Fio. 83. FROM A PREPARATION OF HUMAN TUBERCULOUS SPUTUM, STAINED 



AKTER THE EHRLICH-WEIGERT METHOD. 



The nuclei are stained blue, the tubercle-bacilli pink. Magnifying power 700. 



for twenty-four hours if not heated. After this the prepara- 

 tion is stained for two minutes in a filtered concentrated 

 watery solution of vesuvin, then washed in distilled water. 

 On examination with a yV oil-immersion lens and Abbe's con- 

 denser, it will be found that all the elements are stained 

 brown with vesuvin except the bacilli, which are blue. A still 

 more successful aud more delicate reaction is shown by the 



1 Berliner klin. Woehenschrift, xv. 1882. 



