EXAMINATION OF BACTERIA WITH THE MICROSCOPE. 53 



(d) Alcohol, until decolorized to a faint blue-gray. 



(e) Xylol. 



(f) Mount on a slide in balsam. 



Weigert's Modification of Gram's Method, or Weigert's 

 Stain for Fibrin. (a) Place the section in aniline-water 

 gentian-violet solution, five minutes or more. 



(&) Wash briefly in water. 



(c) Place the section upon a slide by means of a section- 

 lifter; having straightened it carefully, absorb the water 

 with blotting-paper. 



(d) Iodine solution (see page 42) one to two minutes. 



(e) Absorb the iodine solution with blotting-paper. 



(f) Add aniline oil, removing it from time to time with 

 blotting-paper, and adding fresh aniline oil until the color 

 ceases to come away. (Aniline oil serves in this connection 

 both to decolorize and to dehydrate. It absorbs the water 

 rapidly and efficiently. However, on account of its decol- 

 orizing tendency, it must be removed before the specimens 

 can be mounted permanently.) 



(g) Add xylol; remove it with blotting-paper; and add 

 fresh xylol several times, in order to extract the last trace 

 of aniline oil. 



(h) Mount in Canada balsam. 



This method is more convenient for the staining of sec- 

 tions than the Gram method. The results, however, are 

 essentially the same as far as the bacteria are concerned ; 

 fibrin and hyaline material are stained blue, bacteria violet. 

 It is often impossible to decolorize the nuclei completely 

 without decolorizing the bacteria also. The parts of the 

 nuclei which remain stained often present pictures that re- 

 semble bacteria, and which may lead to error if not recog- 

 nized. Basophilic granules also retain the stain, as do the 

 horny cells of the epidermis. These remarks apply also 

 to Gram's method, except as regards fibrin. Very beauti- 



