BLOOD ANALYSIS 



303 



The transparent portion of the cell is directly over a circular opening 

 in the case, through which the blood specimen is viewed by means of 

 the small telescope. 



The semicircular colored glass wedge is so ground that each par- 

 ticular shade of color corresponds to that possessed by fresh blood which 

 contains some definite percentage of hemo- 

 globin. It is mounted upon a disc which 

 may be manipulated by the milled wheel in 

 such a manner as to bring successive por- 

 tions of the wedge in position to be viewed 

 through a circular opening contiguous to the 

 opening through which the blood specimen is 

 viewed. For a further description of the in- 

 strument see Figs. 92, 93, and 94. 



In using the Dare hemoglobinometer proceed as 

 follows : Puncture the finger-tip or lobe of the ear 

 of the subject by means of a needle or scalpel and, 

 after a drop of blood of good proportions has 

 formed, place the flat capillary observation cell in 

 contact with the drop and allow it to fill by cap- 

 illary attraction (Fig. 94). Replace the cell in its 



proper place on the instrument. When in position, a portion of this cell may be 

 observed through a small telescope attached to the apparatus. It is viewed 

 through a circular opening and near this circle is a second one through which a 

 portion of a semicircular colored glass wedge is visible. These two circles are 

 illuminated simultaneously by means of the flame of a candle. The colored glass 



FIG. 93. HORIZONTAL SEC- 

 TION OF DARE'S HEMOGLOBIN- 

 OMETER. (Da Costa.} 



FIG. 94. METHOD OF FILLING THE CAPILLARY OBSERVATION CELL OF DARE'S HEMO- 

 GLOBINOMETER. (Da Costa.} 



may be rotated by means of a milled wheel and the point of agreement of the 

 color of the adjoining discs may be determined in the same way as in FleischPs 

 hemometer. The scale reading gives the percentage of the normal quantity 

 of hemoglobin which the blood sample under examination contains. Compute 

 the actual hemoglobin content in the same manner as from the scale reading of 

 the Fleischl hemometer (see page 299). 



