PREPARATION AND STAINING OF TIS 



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 ani- 

 line-fuchsine solution may also be prepared by the 

 simple plan described for Gram's method (page 60). 

 The more special methods for staining will be given 

 with the description of those species of micro- 

 organisms to which they apply. 



* Watson Cheyne, Practitioner. 1883. 



