190 STUDY OF INDIVIDUAL BACTERIA-STAINING 

 6. Gabbet's (methylene) blue (solution). 



Dry methylene blue ... 4 parts 



Concentrated HiSOi . . . 25 parts 



Distilled water .75 parts 



Dissolve the dry dye in the acid and add the solution to the dis- 

 tilled water and filter. 



Staining solutions are conveniently kept in square drop- 

 ping bottles inserted in a block as shown in Fig. 138. This 

 form of holder necessitates the use of one hand only in secur- 

 ing the stain and dropping it on the preparation. 



Fig. 138. — Author's staining set. Square bottles are set in square holes in 

 the block. The capacity of each bottle is 30 c.o. 



The actual staining of bacteriological preparations can 

 be learned only by repeated laboratory practice, yet the 

 following methods have given such uniform results in class 

 work that it is felt they are not out of place in a text-book. 



Preparation of the "Film." — The author learned to stain 

 bacteria on the "cover-glass" but does not recall having 

 used this method in fifteen years and does not teach it to 

 his students. All staining is done on the slide. To prepare 

 a film from a solid culture medium the procedure is as 

 follows: 



