f ' 



EXAMINATION OF BACTERIA WITH THE MICROSCOPE. 57 



(d) Wash in water. 



(e) Stain with watery solution of methylene-blue half a 

 minute. 



(/) Wash. 



() Dry. 



(h) Balsam. 



The spores are intensely stained by the fuchsin. The 

 stain is removed from everything except the spores by the 

 acid alcohol. The methylene-blue solution stains the bodies 

 of the bacteria, the spores remaining brilliant red. There 

 are various other methods for staining spores, but this pro- 

 cedure gives good results. The principle is the same as in 

 staining the tubercle bacillus, except that more pains are 

 needed to impregnate spores with the dye. 



Staining of Capsules. The capsules which many bac- 

 teria possess, appear to be made of some gelatinous sub- 

 stance, which is difficult to stain. 



Method of Welch. (a) Cover-glass preparations are 

 made in the usual manner. Pour glacial acetic acid over 

 the film. 



(&) After a few seconds, replace with anilin- water gen- 

 tian-violet, without washing in water. Change the stain 

 several times to remove all the acetic acid. Allow it to act 

 three or four minutes. 



(c) Wash and examine in salt solution, 0.8 to 2.0 per 

 cent. 



Bacteria are deeply stained, while their capsules are pale 

 violet. This method has been recommended for staining 

 the capsule of the pneumococcus. 



Methods of Hiss. i. (a) Cover-glass preparations are 

 made in the usual manner, and fixed in the flame. 



(&) Stain for a few seconds in a half-saturated watery 

 solution of gentian-violet. 



(c) Wash in 25 per cent, solution of potassium carbonate 

 in water. 



