WATERY ANILIN STAINS 



107 



FIG. 53 



Wash bottle. 



tion it is best to pour some water from a small bottle or a so-called 

 chemical wash bottle over the preparation so that the washing fluid 

 may run directly into the bichloride solution. 



5. After being washed, drop the cover-glass from the Stewart 

 forceps on a double layer of filter paper; then sterilize the end of the 

 forceps over the flame of the Bunsen burner. 

 Now put aside the forceps and place a second 

 double layer of filter paper over the cover-glass 

 and dry it by pressing on the paper. Pick up 

 the cover-glass carefully at the margin and 

 move it about a little over the flame to get it 

 perfectly dry. Finally, mount in Canada 

 balsam and throw the filter paper used for 

 drying the specimen into the bichloride solu- 

 tion. 



The student should not imagine that staining 

 with watery solutions, air drying, and fixing in 

 the cold kills such bacteria and their spores, 

 as anthrax, tetanus, malignant oedema, etc. 

 He must, therefore, be careful with his cover- 

 glass preparation until it is safely mounted in 

 the Canada balsam. Some bacteria are much 

 more dangerous in the laboratory than out in 



field practice among patients. The glanders bacillus is one of those 

 which has killed a number of laboratory workers, hence it is particu- 

 larly necessary to be careful when handling it in pure cultures. 



Watery Anilin Stains. Besides those already mentioned the fol- 

 lowing watery anilin stains are frequently used : 



LOEFFLER'S ALKALINE METHYLENE BLUE. 



Saturated alcoholic solution of methylene blue 30 c.c. 



Watery solution of caustic potash containing the latter in the very dilute pro- 

 portion of 1 to 10,000 100 c.c. 



This is an excellent all-around dye. It stains cover-glass preparations 

 in from three to five minutes or in even less time; the stain does not 

 decompose easily, and keeps well for many months in a tightly glass- 

 stoppered bottle. 



GRAM'S METHOD OF STAINING BACTERIA. This is a very useful 

 method, because it permits the differentiation of certain kinds of 

 bacteria, which are morphologically so much alike that they could 

 not be distinguished merely by microscopic examination. The fol- 

 lowing solutions are necessary for this stain : 



A. Anilin-water Gentian Violet. Take about nine parts of dis- 

 tilled water and one part of anilin oil. Shake well in a flask or test- 

 tube and filter clear through an ordinary paper filter. Anilin oil is 

 slightly soluble in water. In a saturated solution the excess of the 

 oil shows in oily droplets in the fluid; when filtered these droplets are 



