METHODS OF STAINING TUBERCLE BACILLI. 



41 



at once transferred to alcohol of such a strength, and left there 

 for ten or fifteen minutes, after which they are stained for several 

 minutes with a weak solution of vesuvin or methyl blue. Rinse 

 with sixty per cent, alcohol, and then with absolute alcohol, as 

 for ordinary balsam specimens. In the further preparation of these 

 specimens, Koch objects strongly to the use of clove oil for clearing 

 up the preparations, and advises the use of turpentine or cedar oil, 

 neither of which removes the aniline colour from the specimen. 

 He also advises the use of turpentine as a solvent for the balsam. 

 In preparations treated in this manner, before the second staining 



Fig. 8. — Section of liver. Acute tubercle. Stained with gentian 

 violet. No contrast stain. ( x 400. ) 



a. Section of a small vessel in the portal space. 



b. Connective tissue of portal space. 



c. Enormous masses of tubercle bacilli in the perivascular lym- 



phatics, and also in the lymphatics or connective tissue spaces. 

 Some of the bacilli have been carried into the lumen of the vessel, 

 where they are in contact with the blood corpuscles. This is pro- 

 bably accidental. 



there is not the slightest coloration of the tissues, or at most there 

 is a faint blue tinge, but the tubercle bacilli stand out very pro- 



