Blood Snienrs 210 



ettsia and psittacosis. These foreign elements, in most cases, are best 

 demonstrated \vith a Romanowsky type of stain. 



Blood Smears 



Preparation for Thin Smears 



Slides must be clean for a iniiform smear. Handle slides at the ed2:es, 

 keeping fingers off the clean surface. Prick the finger and when a small 

 drop of blood appears, wipe it away. Touch the next drop of blood to 

 the clean stirface of the riolit end of the slide. Place the narrow edsfe of 

 another slide at about a 20° angle on the first slide and to the left of the 

 drop blood. Pull to the right mitil the slide touches the blood. As soon 

 as the blood has spread along the line of contact, push the right hand 

 toward the left. Push steadily luitil all the blood disappears or the other 

 end of the slide is reached. This method drags the blood but does not 

 run over it and crush some of the cells. The hand can be kept from 

 shaking by resting it on the table. Also do not use a slide with a rough 

 edge to leave streaks in the smear. If the blood seems thick, reduce the 

 20° angle to feed it out at a slower rate. With thin blood increase the 

 angle. (See Peqiieno, 1960, for a clever method using a pen to make 

 thin smears.) 



Dry the slides rapidly in the air; waving them facilitates drying, and 

 prevents crenation (notching or scalloping of edges) of the red cells. 



Preferably blood smears are stained immediately or within 24 hours. 

 If they must be stored, place them in a tight box away from dust and 

 flies. 



Blood smears are commonly stained with a Romanowsky type of 

 stain, or neutral stain (page 110). Neutrality is essential, and therefore 

 dilution usually is made with a buffer solution of a known pW. Dis- 

 tilled water often is too acid, and tap water too alkaline. The smears 

 require no fixation in the usual sense, since Wright's stain (1902) in- 

 cludes both fixing agent (methyl alcohol) and stain. 



Thin Smear Method 



solutions: 



Wright's stain: 



The stain may be purchased in three forms: (1) by the bottle, 10, 25 

 or 100 gms.; (2) in capsule form, 0.1 gm. per capsule; or (3) in solu- 

 tion, 4, 8 or 16 ounces. 



