14 



METHODS OF EXAMINATION 



age scale is etched into the edge of a corresponding semicircle of 

 glass and is placed directly opposite the standard scale. These 

 semicircular plates are fastened to a white disc and are protected 

 by a circular rubber case. The standard is rotated by a milled 



head placed on the upper 

 part of the case. The speci- 

 men of blood is compared 

 with the standard scale 

 through two small holes 

 horizontally placed and 

 viewed through a camera 

 tube, the eyes of the oper- 

 ator being protected from 

 the light by a shield. Light 

 is afforded by a candle at- 

 tached to the instrument. 



Method of using. The in- 

 strument is prepared for use 

 by screwing the camera tube 

 into place and rotating the 

 shield so that the two holes 

 through which the blood and 

 standard scale are viewed 

 are uncovered. The candle in its holder is then placed in 

 position. The candle wick should be straight or the candle 

 rotated so that it will illuminate both apertures equally. The 

 pipette is removed from the instrument. It should be scrupulously 

 clean and dry. The pipette is filled by touching it, plain glass 

 uppermost, to a drop of blood. As soon as it is rilled it is placed 

 in position. It is not necessary to wipe blood from the edges of 

 the pipette, none should however be on the surface of either of the 

 plates. The instrument is held horizontally and should be pointed 

 toward a dark surface. Comparison is made by rotating the milled 

 head, making rather quick turns. When the tint of the standard 

 scale is made to exactly match that of the blood the hemoglobin 

 value is read from the edge of the instrument, the reading being 

 the one indicated by the beveled edge of the opening. 



Dare's instrument gives the amount of hemoglobin with greater 

 accuracy than Tallqvist's or Gower's. It has given in my ex- 



FlG. 8. Dare's hcmoglobinometer. ' 



