VACCINE-THERAPY 27 



This form of spreader will be found to be most useful in the 

 making of blood-films and in counting bacteria against the 

 blood-corpuscles when we desire to make a standardized 

 emulsion. When dealing with pus only, it is necessary to 

 put a drop on the end of a slide and spread it. If it is too 

 thick, a little distilled water or normal saline solution 

 should be added. Needless to add, to get a perfectly even 

 spread, a clean, grease-free slide should be used. The film 

 so made is now allowed to dry, and fixed by heat sufficient 

 to coagulate the albumin and to retain the bacteria. This 

 heating should be done by passing the slide through the 

 flame of the spirit lamp (specimen face upwards) two or 

 three times, and made just hot enough to bear comfortably 

 on the back of one's hand. The chosen stain is now 

 filtered on to the slide through filter-paper, then washed 



Fig. 16.— Cornet Forceps. 



in tap-water, dried with filter-paper, and completely dried 

 over the flame. In the same way cover-glasses are stained, 

 holding them with cornet forceps. 



Usual Method of Fixing Films. 



1. The simplest method of fixing a film to a slide or 

 cover-glass is to pass it through the flame of a Bunsen 

 burner (specimen side uppermost) three or four times. In 

 this case the albuminous elements are coagulated by 

 heat. 



2. Absolute alcohol fixes a specimen in five to ten 

 minutes. 



3. Corrosive sublimate (a saturated aqueous solution) 

 fixes in two to three minutes, and even less in some 

 cases. 



