34 ESSENTIALS OF BACTERIOLOGY. 



CHAPTER V. 



GENERAL METHOD OF STAINING SPECIMENS. 



Cover-Glass Preparations. The material is evenly spread in 

 as thin a layer as possible upon a cover-glass ; then, to spread 

 it still more finely, a second cover-glass is pressed down upon 

 the first and the two slid apart. This also secures two speci- 

 mens. Before they can be stained they must be perfectly dry, 

 otherwise deformities will arise in the structure. 



Drying the Specimen. The cover-glass can be set aside to dry 

 or held in the fingers over the Bunsen burner (the fingers prevent- 

 ing too great a degree of heat). Since most of the specimens 

 contain a certain amount of albumenoid material, it is best in 

 all cases to " fix" it, i. e., to coagulate the albumen. This is 

 accomplished by passing the cover-glass (after the specimen is 

 dry) three times through the flame of the burner, about three 

 seconds being consumed in doing so, the glass being held in a 

 small forceps, smeared side up. 



The best forceps for grasping cover-glasses is a bent one, bent 

 again upward, near the ends. * 



The object is now ready for staining. 



Staining. A few drops of the staining solution are placed 

 upon the cover-glass so that the whole specimen is covered, 

 and it is left on a few minutes, the time depending upon the 

 variety, the strength of stain, and the object desired. Instead 

 of placing the dye upon the object, the cover-glass can be im- 

 mersed in a small glass dish containing the solution ; or, if 

 heat is desired to intensify or hasten the process, a watch- 

 crystal holding the stain is placed over a Bunsen burner and 

 in it the cover-glass ; and, again, the cover-glass can be held 

 directly in the flame with the staining fluid upon it, which 

 must be constantly renewed until the process is completed. 



Removing Excess of Stain. The surplus stain is washed oil* 

 by dipping the glass in water, distilled water always best, 

 though ordinary running water is admissible. 



The water is removed by drying between filter paper or 



