254 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



some glass beads or balls, or fragments of glass of any sort, and 

 shake for ten minutes. This will break up the coagulum and set 

 most of the cells free. Allow the fluid to stand for a minute or 

 two so that the pieces of fibrin may settle ; then decant the 

 supernatant fluid into the centrifugalizing or sedimenting tube, 

 and proceed as before. This process is not altogether satisfactory, 

 and it is better in all cases to mix the fluid to be examined, at 

 the time of withdrawal, with its own volume of (roughly) 5 per 

 cent, sodium citrate, which prevents subsequent clotting. 



Where the fluid is pus no preparation is usually necessary. If 

 it clots it does so very feebly, and in this case a little stirring 

 with a platinum loop will set free plenty of cells for examination, 

 or you may take up the clot with a loop and rub it on the slide or 

 cover- glass. 



Method of preparing the Specimen for Examination. — 

 The specimens may be examined wet or dry. In most cases the 

 former method is best, as it is quicker, and often yields information 

 which cannot be obtained by a dry specimen. The preparations, 

 however, do not keep, and where permanent ones are required 

 the method is inapplicable. 



Wet Method. — Place one drop of watery methylene blue or 

 borax methylene blue on a slide and add two or three drops of 

 the emulsion of cells. Stir with the platinum loop or needle, 

 allow the mixture to stand for two or three minutes, and then 

 apply a cover-glass. The cover-glass may be cemented to the 

 slide by means of melted paraffin applied with a hot iron rod ; it 

 is best to do this if the oil-immersion lens is to be used, otherwise 

 the suction of the lens may lift up the cover-glass. 



Or, put two or three drops of the emulsion on a slide, cover, 

 and examine without staining. Then put a drop or two of acid 

 methylene blue (see p. 31) on the slide just touching the cover- 

 glass ; it will pass in by capillarity, and at different distances 

 from the edge you will get an unstained area, an area where the 

 stain is faint, but very selective, and a deeply stained area. The 

 middle zone is best to examine. The red corpuscles, if present, 

 will be dissolved by the acid, and after a few minutes the cells 

 will be stained with great distinctness. 



Dry Method. — Prepare films on the slide or cover-glass 

 (p. 218), using the emulsion exactly as if it were blood. This 

 may be stained by Jenner's method (p. 224) or fixed and stained 

 subsequently. Any of the fixing and staining methods described 



