HISTOLOGICAL EXAMINATION 17 



thoroughly clean. Unused slides may be cleaned in strong soap 

 or "gold dust" solution, well rinsed in water, then placed in al- 

 cohol from which they are wiped and polished. Slides with ground 

 edges are preferred. The edge of a slide is touched to the top of a 

 fresh drop of blood then 

 applied to another slide 

 at an angle o f about 

 forty degrees (Fig. 10). 

 As soon as the blood has 

 spread along the line of 

 contact of the two slides, 

 t h e smearer is drawn FlG _ 10- Spreading film on glass slide, 

 along with very gentle 



pressure slowly leaving a thin smear of blood on the other slide. 

 The smear should cover one-half or two-thirds of the slide. A little 

 practice will enable one to make good smears at each attempt. 

 The smears may be kept for some time without altering their 

 staining properties if they are kept dry. After several weeks, 

 however, not so good results can be obtained from certain of the 

 more delicate stains, Jenner's, Wright's and Hasting's. 



Fixation and staining. Jenner's stain is one of the most rapid 

 and easy to manipulate of the many methods in use and stains 

 each of the several kinds of granules in the leucocytes. It is rec- 

 ommended for ordinary examinations. The staining fluid is a 

 five-tenths per cent, solution of the dye (Gruebler's) in pure methyl 

 alcohol (Merck's). This acts as both fixing and staining fluid. 

 The smear, previously unfixed, simply dried in the air, is flooded 

 with the staining fluid which is allowed to act two or three minutes, 

 when it is washed in distilled water until the better spread portions 

 have a pinkish tint, which usually requires about ten seconds. 

 The water should then be shaken and blown vigorously from the 

 specimen which is then dried rapidly in the air. As soon as it is 

 thoroughly dry it. may be examined using a two mm. (j^ in.) oil 

 immersion objective. It is not necessary to place a cover glass 

 on the specimen as the index of refraction of homogenous oil is 

 the same as that of glass. If a dry objective should be used a 

 cover glass would be necessary; but as high a magnification as 

 that given by a two mm. (y 1 ^ in.) objective is needed. The stained 

 films keep as well without being covered as when mounted in 



