PREPARATION OF FILMS. l6l 



2. Two pair of dissecting forceps. 



3. A needle for taking blood. 



4. A platinum loop having a diameter of about one- 

 tenth of an inch is sometimes useful, especially to a 

 beginner. 



Method. The patient having been pricked and the 

 first drop of blood wiped away, take up a cover-glass in 

 one pair of forceps, holding the glass by its corner, and 

 touch the drop of blood with it. In doing so take great 

 care not to touch the patient's skin. There should now 

 be a small drop of blood in the very centre of the cover- 

 glass. This is the difficult step ; you must not get too 

 much nor too little blood, or the films will be useless. 

 Now take up the second cover-glass in the other pair of 

 forceps and place it on the top of the drop in such a 

 position that the corners of the two cover- glasses do not 

 correspond. Release the upper cover-glass ; it will ap- 

 proach the lower one, being drawn thereto by the 

 capillary attraction caused by the presence of a small 

 quantity of fluid between the two. 



At this stage you will see whether you have taken the 

 right amount of blood or no. If you have, the drop will 

 spread out, still retaining its circular shape, until it 

 approaches the octagon formed by the intersecting 

 edges of the two cover-glasses ; if you have taken too 

 little it will not reach so far ; and if you have taken too 

 much it will extend further and the upper cover-glass 

 will float loosely on the lower. 



It is necessary to lay great emphasis on the fact that 

 the cover-glasses must not be squeezed together, but 

 must simply come together by capillary attraction. 



When the drop has ceased to spread take hold of the 

 upper cover-glass with the forceps at a corner opposite 

 to that of the lower cover-glass which you are still 



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