10 METHODS OF EXAMINATION 



cautions and is drawn into the pipette to the mark {, £ or ^. 

 Diluting fluid, a filtered one per cent, solution of sodium car- 

 bonate, is drawn up to the mark as in the hematocytometer. It 

 is well shaken, and the diluting fluid expelled from the long arm 

 of the pipette. Then one compartment of the mixing cell is filled 

 with the diluted blood, the other compartment filled with water, 

 the glass disc slid into place and the metal cap adjusted. The 

 cell is placed in position on the stage so that the part containing 

 water is over the colored wedge. Comparison should be made 

 by the light of a candle or petroleum lamp placed at some distance 

 from the hemometer. A better result will be obtained in match- 

 ing the blood and scale by moving the scale by short quick move- 

 ments. 



A table accompanies each instrument in which is given the 

 number of grams of hemoglobin corresponding to the reading 

 obtained with that instrument. The Fleischl-Miescher hemom- 

 eter is one of the most accurate of those used for obtaining the 

 amount of hemoglobin. The feature of being able to get the 

 number of grams of hemoglobin is a very desirable one and should 

 be given in all hemoglobinometers. It is more reasonable to learn 

 the amount of Hb, given in grams per 100 cc. of blood, than the 

 percentage of a supposed normal, which is fixed at different values 

 in different makes of hemoglobinometers. 



HISTOLOGICAL EXAMINATION 



For histological examination blood is examined fresh and in 

 fixed and stained preparations. Fresh preparations are made 

 by touching the center of a thoroughly clean cover glass to the 

 top of a freshly exuded drop of blood then dropping the cover 

 gently on a clean slide. If a proper sized drop is obtained the 

 blood will spread between the cover and slide in a thin layer. The 

 cover glass should not be pressed down as pressure may rupture 

 or distort the red corpuscles. If it is desired to keep the specimen 

 longer than a few minutes the edges of the cover glass should be 

 sealed with liquid paraffin or castor oil. 



For fixed and stained preparations the blood should be spread 

 in a thin smear. The method of making smears on glass slides 

 will be found a simple and convenient one. The slides should be 



