LV. Examination of fresh blood. 



1. Appliances. Microscope; one twelfth inch oil-immersion 

 lens; 22 mm. cover glasses; slides; saddler's needle and 

 holder; clean piece of old muslin one-half meter square; 

 paper and pencil. 



2. Preparation. Clean cover glasses and slides as follows: 

 Immerse in 60% acetic acid, then wash in soap and 

 water and place in dilute alcohol; just before using, 

 wipe dry and place under a bell-jar; the needle should 

 be so placed in the holder that it protrudes one-fourth 

 to one-third inch. 



A convenient needle-holder, the exact size of which 

 is shown in Fig. 36, may be obtained from a dental sup- 

 ply house. 



FIG. 36. 



A medium saddler's needle may be obtained from a har- 

 ness shop. If too long, it can be broken and the point 

 used. These needles have three cutting edges so that 

 blood flows easily from a puncture made by one. 

 Operation. Wipe the lobe of the ear with a damp 

 cloth; then briskly with a dry cloth; seize the lobe 

 with the left ringer and thumb quite tightly; thrust 

 the needle into the ear with a quick stroke. Wipe 

 away the first drop; then when the second drop has 

 become a little more than one eighth of an inch across 

 its base, bring the center of the cover glass under 

 the drop and touch the lower part without touch- 



259 



