SMEAR PREPARATIONS 97 



to dilute the material so as to obtain a thinner film. If a 

 specimen is to be made from an organ, a particle of the 

 pulp is picked up and an emulsion made as before, or a 

 small piece of the organ may be held in sterile forceps and 

 the cut surface gently smeared over the slide or cover- 

 glass, which is then similarly dried and fixed ; these are 

 termed " smear preparations." 



To obtain the best results it is preferable before staining 

 to submit films of blood 1 or pus or smear preparations to 

 the action of some chemical fixing agent, unless the film 

 is stained with Leishman's solution, which both fixes and 

 stains. The simplest method of doing this is to immerse 

 the films, after owr-drying, in a mixture of equal parts of 

 absolute alcohol and ether for ten to thirty minutes. In 

 hot countries a saturated aqueous solution of corrosive 

 sublimate (five to fifteen minutes) is perhaps as satisfactory 

 as anything. Another method, combining both fixing and 

 staining, is to immerse the films as soon as they are pre- 

 pared and without drying for a few minutes in the following 

 solution : 



Absolute alcohol, saturated with eosin . . 25 c.c. 



Pure ether ....... 25 c.c. 



Alcoholic solution of corrosive sublimate (2 grm. 



in 10 c.c.) ....... 5 drops 



The specimens are then removed with a forceps and well 

 rinsed in water, stained for not more than a minute in a 

 saturated aqueous solution of methylene blue, washed 

 quickly, dehydrated in absolute alcohol, cleared in xylol, 

 and mounted in xylol balsam. This solution may be 

 used for fixing blood, pus, sputum, etc., if the eosin be 

 omitted, and the preparations may then be stained or 

 otherwise treated in any desired manner. 2 



1 For the method of preparing blood-films see the section on " Ma- 

 laria," Chapter XVIII. 



2 Gulland, Brit. Med. Journ., 1897, vol. i, p. 65. 



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