58 BACTERIOLOGY. 



result is obtained by placing the sections for a few 

 minutes in Orth's solution (picro-lithium-carmine) ; 

 transferring to acidulated alcohol, then to an alco- 

 holic solution of picric acid, and treating with clove- 

 oil and balsam (Plate XVII., Fig. i). 



Weigert-Ehrlich Method. This is a method 

 in which nitric acid is employed as a decolorising 

 agent. It is as follows : Filtered, saturated, watery 

 solution of aniline one hundred parts ; saturated 

 alcoholic solution of a basic aniline dye (methyl- 

 violet, gentian-violet, fuchsine), eleven parts; are 

 mixed and filtered. Rapid staining is obtained by 

 warming the solution. Decolorise with nitric acid 

 (i in 2), and stain with a contrast colour. As 

 delicate sections are apt to be injured by immersion 

 in the nitric acid, they may be transferred from the 

 fuchsine solution to distilled water, then rinsed a 

 few minutes with alcohol, and finally placed in the 

 following contrast stain for one to two hours : 



Distilled water . . . 100 cc. 



Saturated alcoholic solution of 



methylene blue. . , 20 cc. 



Formic acid . . . . 10 mm. 

 The method of Weigert-Ehrlich is employed for 

 staining both leprosy and tubercle bacilli. The 

 more especial methods which have been employed 

 by Koch, Klein, Gibbes, Friedlander, Schutz, Lust- 

 garten, and others will be given with the descrip- 

 tion of those species of micro-organisms to which 

 they apply. 



