FIXATION OF BLOOD FILMS. 165 
about five minutes—slides requiring a slightly longer 
time than cover-glasses. 
The ideal way is to use a dry air steriliser (see p. 8) 
to place the films in it whilst cold, to heat up to 150°C., 
and then to turn out the gas. In the absence of this 
apparatus a metal slab or plate such as has been 
recommended for use in staining the tubercle bacillus 
answers well. It is mounted upon a tripod stand 
and the heat applied at one end. After a time the 
temperature of various portions of the plate are tested 
by the application of a few drops of water; the point at 
which the drop assumes the “spheroidal state” (i.¢., 
takes the form of a sphere and does not wet the plate) 
is about the right point to use. The slides or films are 
placed at this point for the appropriate time. 
II. Frxation py ALCOHOL AND ETHER. 
This is very simple; the films are placed in a mixture 
of equal parts of alcohol and ether for at least half an 
hour. 
This method of fixation is perhaps the best that can 
be adopted for general purposes. 
III. Fixation By ForRMALIN. 
There are several methods by which the fixative 
action of formalin can be used for blood work. Of 
these the use of a mixture of one part of formalin with 
nine parts of absolute alcohol answers perfectly. The 
films are immersed in this for half a minute and then 
washed thoroughly under the tap. 
This method of fixation is both good and rapid. 
