78 CLINICAL MICROSCOPY AND DIAGNOSIS. 



Microscopic Examination of Blood Films. 



(«) Direct examination of moist films is called for, 

 in determining poikilocytosis, leucocytosis, and in ex- 

 amining for the malarial Plasmodium. 



Moist prepaiations are made by touching the blood 

 drop with a thoroughly clean cover glass, and then in- 

 verting this upon a slide. Only a small drop must be 

 taken on the cover glass so that it will spread out in a 

 single layer on the slide. To prevent drying, the cover 

 glass may be ringed with vaseline. 



(b) Examination of films dried and stained, is of 

 much wider application, being employed to determine 

 the same characters as the moist films, and in addition 

 giving the forms and relative proportions of the white 

 cells and the staining characters of the red corpuscles. 



The blood films are prepared by touching one cover 

 glass to the blood, so as to obtain a small drop, then 

 dropping on this cover glass a second, and sliding the 

 two apart. The films are dried in the air and are then 

 ready for fixation. This may be effected by heat or in 

 certain fixing fluids. Heat fixation gives the best 

 results. The cover glasses may be placed in an oven 

 for 2 hours at a temperature of 110°C. As this 

 method cannot always be carried out, a cheap and effec- 

 tive substitute, is made by the use of a long triangle of 

 brass, about .5 cm. in thickness. A gas or spirit lamp 

 flame is applied to the apex and after 5 or 10 minutes 

 tests are made for the boiling point on the triangle. 

 The cover glasses are placed 2 to 3 cm. in front of this 



