2O 



To LABEL FILMS 



Films should always be labelled as soon as possible, 

 otherwise uncertainty and annoyance are sure to arise. 

 The use of labels is not absolutely necessary. 



1 . The most convenient method is that of writing 

 on the slide with ordinary ink, which should be quite 

 dry before placing in alcohol ; there is then no fear of 

 the ink coming off. 



2. After making a dry film, as described above, 

 the name, date, and other necessary information, are 

 scratched on the film with the head or point of the 

 needle. (Powell). 



To Fix FILMS 



Films must always be fixed, but this may be 

 omitted where the stain also contains the fixative, e.g., 

 in the Leishman and Jenner stains. 



1. Absolute alcohol. This is the most convenient 

 fixative. It is best kept in a glass-stoppered cylindrical 

 jar about two inches in diameter. Methylated spirit 

 can be used instead. Fix for three minutes or longer. 



2. Heat. For the study of leucocyte granules 

 this mode is indispensable. Place a crystal of urea 

 (M. Pt. 131 C.) on the film to act as an indicator. 

 Heat over a flame until the crystal just fuses. Allow 

 to cool and remove the urea. The slide is then fixed. 

 An alcoholic stain must still be used, e.g., Jenner, 

 Ehrlich, etc. (or the haemoglobin will be dissolved 

 out), but not Romanowsky, Giemsa or other watery 

 stains. 



3. For other methods, and especially for the 

 fixing of ' wet films,' vide ch. xxxiv. 



