BACTERIOLOGICAL DIAGNOSIS 1 29 



practice will enable one to tell when fixation is complete 

 without overheating, (i) Ovens. Slides may be placed in 

 an oven provided with a thermometer and exposed to a tem- 

 perature of from 110° to 150° C. from 5 to 10 minutes. 



2. By alcohol. Fix in from 95% to 97% alcohol from 10 

 to 30 minutes. If left too long in alcohol they do not stain 

 so well. For staining malarial parasites, fixation by alcohol is 

 preferable. 



Method of using the stain. Put the stain in a Petri dish, 

 place in it two or three toothpicks, matches with heads 

 removed, or pieces of small glass rod to support the slides, 

 and place them, specimen side down, in the stain upon this 

 support. This allows any precipitate to settle away from 

 rather than upon the slides. Allow the stain to act one or 

 two hours. They will not overstain in twenty-four hours. 

 Wash in water and when _ dry they are ready to examine 

 without a cover glass. Immersion oil can be applied directly 

 to the films v.-ithout injury. 



