54 ESSENTIALS OF BACTERIOLOGY 



ated methyl-alcohol solution is filtered and further diluted 

 with methyl-alcohol. The stains are used in very dilute 

 form. Where the blood-films or exudates are not first fixed 

 in alcohol, the concentrated stain is allowed to cover the 

 preparation for five to twenty seconds to fix; then water is 

 poured on to dilute and from five to fifteen minutes allowed 

 for staining, the excess removed with water. The stains can 

 be purchased in powder or tablet form, and need only be 

 mixed with methyl-alcohol to be ready for use. 



CHAPTER VII 

 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 specimens. 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 preventing too great a degree of heat). Since most of 

 the specimens contain a certain amount of albuminoid mater- 

 ial, it is best in all cases to "fix" i. e., to coagulate the 

 albumin. 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 so doing, 

 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 (Fig. 13). It prevents the 

 flame or staining fluid from reaching the fingers. 



The object is now ready for staining. 



Staining. A few drops of the staining solution are placed 



