MICROSCOPIC EXAMINATION 12$ 



blood on the cover-glass near the edge. Take a thick, square 

 cover-glass by the edge, rest it on the first above the 

 drop of blood, hold it at an angle of about 20 from it, 

 and draw it down over the first, thus spreading the blood in 

 a very thin, even film over the surface. If the film is thick, 

 the preparation should be rejected and another made. Some 

 prefer slides to cover- glasses for this purpose, (d) From 

 milk cultures. Spread as thin a film of the milk culture as 

 possible on the cover- glass and allow it to dry in the air. Im- 

 merse the preparation in a watch glass or other receptacle 

 containing a few cubic centimeters of ether and absolute 

 alcohol in equal parts, which dissolves out the fat and fixes 

 the film to the cover-glass at the same time. Then remove 

 and, after the ether and alcohol have evaporated, stain as 

 usual. The amount of albumen in the milk will usually 

 cause a heavy background, which will require decolorizing 

 with alcohol or weak acetic acid, (e)- From pus. Spread 

 as thin a film of the pus as possible on the cover-glass. (Slides 

 may be used if preferred.) This can be readily done by 

 drawing the edge of a square cover- glass or slide over the 

 surface of another cover-glass or slide on which a bit of the pus 

 has been placed. (/) From sputum. These are usually made 

 for the examination of tubercle bacteria, streptococci and the 

 organisms associated with pneumonia. Select the little yel- 

 lowish-colored masses, if present, remove them by means of 

 fine forceps or platinum loop, and spread them on the cover- 

 glass in a thin layer. If the sputum is homogeneous, make the 

 preparations the same as from cultures, using a small loopful 

 of the liquid. If the sputum is viscid, it is necessary to use 

 the forceps to spread the film on the cover-glass. When dry, 

 the films are fixed by passing the preparations through the 

 flame, after which they are ready to be stained. Slides may 

 be used instead of cover-glasses. Good results follow by dis- 

 solving the sputum in a weak solution of antiformin, centri- 

 fuging, and examining the sediment for tubercle bacteria. 



Staining bacteria in cover-glass preparations, (a) 

 With alkaline metkylene blue. With the pipette place a few 



