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.e., 

 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. FIXATION BY 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 FORMALIN. 



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. 



