Methods of Determination of Pathogenic Microbes. Ill 



Absolute alcohol, .... 1 cub. cent. 



Saturated alcoholic solution of gentian 

 violet, . . . . . 1 " « 



Cover glasses remain in this fluid five minutes, sec- 

 tions fifteen, after which they are transferred for one 

 to two minutes into Gram's solution of iodine in iodide 

 of potassium which consists of: 



Iodine, ...... 1 gram. 



Iodide of potassium, . . . 2 grams. 



Distilled water, .... 300 grams. 



They are then completely decolorized in absolute 

 alcohol, and the ground-work of the preparation 

 stained red (eosin, picro-carniine) or brown (bismark 

 brown, etc.) The violet remains fixed on the mi- 

 crobes, but in the tissue elements it is replaced by 

 the red or brown. 



Weigert's method. — Weigert's violet consists of: 



Saturated aqueous solution of methyl violet 



6 B, . . . . . . 68 grams. 



Absolute alcohol, .... 11 grams. 



Aniline, . . . . . . " 3 grams. 



Sections are stained from five to ten minutes, im- 

 mersed for one to two minutes in Gram's iodine 

 solution, passed rapidly through absolute alcohol (a 

 few seconds) in order to remove the greater part of 

 the water, and decolorized in aniline oil ; they are 

 then cleared in xylol and mounted in balsam. Since 

 by this method contact with alcohol is avoided, it is 

 necessary to stain the groundwork of the preparation 

 in red or brown before staining with violet. This 

 inversion may also be employed without inconven- 

 ience in staining by the Gram method. The employ- 

 ment of alcohol in dehydrating may be entirely 



