34 



VACCINE AND SERUM THERAPY. 



been thoroughly mixed after incubation, is placed. Then a 

 slide with a smooth edge is made into a spreader by breaking 

 off a corner. This is done so that the two margins of the spread 

 shall be on the slide instead of running over the edges of the same. 



FIG. 10. 



The narrowed end of the spreader is now touched to the slide 

 and the drop of blood allowed to run to the under edges of the 

 spreader. The spreader, held at an angle of about 35 to 45 

 is drawn over the slide as is indicated in Fig. 10. The spread 

 on the slide will have an outline as is indicated in Fig. 11. 



The different steps taken in making the spread are essential 

 to secure good smears. When the spreader is pressed firmly 

 enough against the slide while it is being drawn over the same, 



FIG. 11. 



the polynuclear leucocytes, being larger than the red blood cells, 

 will slide out at the edge of the spreader or be drawn to the end 

 of the spread. Care must be taken not to make the smear too 

 thin. 



FIXING AND STAINING OF THE SMEARS. 



After the smear has been made it must be fixed and stained 

 for examination. Fixing and staining is usually accomplished 

 by the ordinary blood stains, Irishman's, Wright's, Jenner's all 

 giving good results, except when the index for the tubercle bacillus 

 is to be determined. The writer, however, has gotten more sat- 



