THE BLOOD. 



247 



seconds the rubber tube is withdrawn, and while the glass tube is yet full of 

 the gas, it is closed with the thumb and gently shaken so as to convert all the 

 hemoglobin into carbon-monoxid hemoglobin. This is then diluted very 

 gradually as in the employment of the Gowers apparatus until the tint of 

 the solution in B corresponds to that in A. The level at which this is 

 observed indicates the percentage of hemoglobin in the blood used. The 

 error in this method scarcely exceeds i per cent. 



, FIG. 107. VON FLEISCHL'S HEMOMETER. K. Red colored wedge of glass moved by R. 

 G. Mixing vessel with two compartments, a and a'. M. Table with hole to read off the percentage 

 of hemoglobin on the scale P. T. Pinion to move K. S. Mirror of plaster-of-Paris. 



Von Fleischl's hemometer consists of a metallic cell divided into two 

 compartments, a and a', by a vertical partition (Fig. 107). In the former 

 a definite quantity of blood is placed and diluted with a known quantity of 

 water. Beneath the compartment a' is placed a glass wedge stained with 

 the golden purple of Cassius or similar pigment, the color of which passes 

 from a deep red at one end to clear glass at the other (Fig. 108). To the 

 side of this wedge is placed a scale 

 ranging from o to 120. By means of 

 the screw, R T, the glass wedge is 

 moved until the color of the glass and 

 diluted blood is identical. The illum- 

 ination of the blood and glass wedge is 

 accomplished by lamp-light reflected 

 from the white reflecting surface 

 beneath. The depth of color of the 

 glass opposite 100 on the scale corresponds to that of normal blood. If, 

 therefore, the colors are identical at 75 divisions, the blood contains but 75 

 per cent, of the normal amount of hemoglobin. 



Absorption Spectra. Both oxyhemoglobin and reduced hemoglobin, 

 like other soluble pigments, have an absorbing influence on certain waves 

 of light, and hence give rise to absorption bands which can be studied 



FIG. 108. TINTED GLASS WEDGE or THE 

 VON FLEISCHL HEMOMETER. 



