46 MANUAL or BACTERIOLOGY. 



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. 



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

 of gentian-violet. 



(c) Wash in solution of potassium carbonate in water. 



(d) Mount and study in the same. 



2. (a) Cover-glass preparations are made and fixed in the 

 ordinary way. 



(6) Use the following stain, heated till it steams: 



Saturated alcoholic solution of gentian-violet or fuchsin . . S c.c. 

 Distilled water 95 c.c. 



(c) Wash in 20 per cent, solution of cupric sulphate. 



(d) Dry and mount in Canada balsam. 



The methods of Hiss are recommended to be used for bacteria 

 that have been cultivated on media containing blood-serum. 

 They have shown that many streptococci have capsules. The 

 writer has had good success from the latter method, with 

 preparations of the pneumococcus from animal tissues. 



Staining of Flagella. — FlageUa are among the most difficult 

 of all objects to stain. The best-known method is that of 

 Loffler. It is important to use yoimg cultures, preferably on 

 agar. 



(a) A small portion of the culture is mixed on a cover-glass 

 with a drop of water. The preparations must be exceedingly 

 thin. The mixing must be done with care in order not to break 

 off the deUcate flagella. The cover-glass must be perfectly 

 clean (see page 25). 



