110 GUIDE TO THE STUDY 



supernatant fluid is carefully poured off and replaced by fresh. 

 The preparation is then put in an oven at 50°C. for a day or two, 

 by which time the alcohol will have been evaporated and the 

 fecal material evenly distributed through the glycerine. At 

 laboratory temperatures this will, of course, require longer 

 exposure and protection from dust. For mounts, a small drop 

 of the sediment is placed in a small quantity of warm glycerine 

 jelly on a slide, stirred carefully to distribute it, and the whole 

 sealed with Noyer's lanoline cement. 



PREPARATION AND STAINING OF BLOOD SMEARS 



Preparation. — Slides and covers must be especially cleaned 

 before using for the preparation of blood smears, or of fecal 



Fig. 33. — Method of making a blood film by pulling a drop of blood behind second 

 slide. (After Daniels.) 



smears for the study of intestinal Protozoa. Pass slides over a 

 flame to remove excess moisture and grease. 



Experience in the preparation of films and in the use of blood 

 stains is best gained with human blood. Wipe the finger with 

 alcohol and prick it with a sterile needle or spring lancet until free, 

 easy drops issue forth. Wipe away the first drop with sterile 

 cotton and select one a little larger than the head of a pin. 

 Touch this with the end of a clean slide to be used as a "pusher" 

 as illustrated by Fig. 33. Place this at an angle of 45 deg. near 

 the end of a clean slide held horizontally. The drop should 



