426 PHARMACEUTICAL BACTERIOLOGY 



exhibit of the kind above specified, the following brief instructions in 

 making microscopic mounts, are given. 



i. Smears. Slide mounts for microscopica 1 examination, generally 

 known as smeais, may be made fiom a great variety of substances, more 

 especially from liquid, semiliquid and pasty mateiials, including blood, 

 sputum, pus, urinary sediment, feces, excretions and secretions, bacteria 

 and bacterial cultures and all substances containing bacteria, etc. 

 Temporary smears may be made of fats, butter, oleomargarine, oils, cieam, 

 and oily substances generally. Permanent smear slides intended foi the 

 exhibit aie to be made as follows. Clean a slide very carefully by means 

 of alcohol and a clean cloth, passing it through the flame of a Bunsen 

 burner after the wiping. Spread the substance very thinly and evenly 

 upon the middle portion of the cleaned slide and allow it to air dry (very 

 moderate heat may be used, not to exceed 7oC.). Next "fix" the smear 

 upon the slide by passing it through the flame of the Bunsen burner four 

 or five times, or, by adding a drop of alcohol. The heat (or the alcohol) 

 coagulates the albuminous matter which may be present, and sticks the 

 objects firmly to the surface of the slide. 



The air dried and "fixed" smear may now be examined and if the 

 mount proves satisfactory (spread sufficiently thin to make details dis- 

 tinct, etc.), it may be labeled and filed away. No cover glass or mounting 

 medium is used. Or, it may be stained by means of methyl ene blue, 

 LoefHer's methylene violet, Fuchsin, Safranin, Bismarck brown, Wright's 

 stain, Giemsa's stain, etc. The selection of the stain will depend upon the 

 object it is desired to attain. The staining should be omitted until it is 

 known for a certainty that staining is desirable and the operator knows 

 how to use it. The unstained mounts will keep indefinitely and may be 

 stained any time. The only difficulty lies in the fact that since the smear 

 mounts are to be examined by means of the 3^2 oil immersion lens, the 

 oil used (cedar oil) would interfere more or less with the staining. 



A blood smear requires special manipulation. Place a droplet of the 

 blood (or the liquid containing the blood) upon a thoroughly cleaned slide, 

 nearer one end. Now place one end of a second cleaned slide just beyond 

 the droplet, at an angle of 30 40, lower the end until the surface of the 

 tilted .slide comes in contact with the droplet, and then gently draw it 

 forward over about % of the slide surface (that is, the slide holding the 

 droplet). Another method for spreading is as follows. Place the second 

 tilted slide on the other side of the droplet, lower until it comes hi capil- 

 lary contact with the droplet and then push it over the surface of the first 

 slide, instead of drawing it forward, as in the first method. After spread- 

 ing, the smear is allowed to air dry and then fixed by means of a drop of 

 alcohol, instead of heat. The stains generally used for blood smears are 



