192 THE BLOOD 



quantity of the blood to be tested plus a definite amount of water. A glass wedge 

 is situated beneath the other compartment, stained in different reds to correspond 

 to the color of different solutions of hemoglobin of known concentration. This 

 scale is then moved onward until its color corresponds precisely with that of the 

 sample of blood. Thus, if the colors are matched, say, at division 75 of the scale, 

 the blood contains only 75 per cent, of the normal quantity of hemoglobin, Mies- 

 cher has endeavored to obviate the use of solutions and has succeeded in producing 

 an instrument of even greater precision than that of Fleischl. Gower^s hemoglo- 

 hinometer^ which is the one most commonly employed to-day, consists of two iden- 

 tical glass tubes, A and B (Fig. 106). Tube A is filled with glycerin-jelly to which 

 picrocarmin has been added until its color corresponds precisely to that of a 1 

 per cent, solution of hemoglobin, i.e., to that of normal blood'diluted 100 times. 

 Tube B is filled with 20 cu. mm. of blood to which a few drops of distilled water 

 have been added to prevent coagulation. Water is then dropped into this re- 

 ceptacle by means of a pipet until the color of the diluted blood corresponds pre- 

 cisely with that of the standard solution in tube A. The gradations upon tube -B 

 accurately represent the percentage of hemoglobin. It is necessary to transpose 

 the tubes repeatedly. Thus, if the original 20 cu. mm. of blood are matched at 

 division 80, the blood contains but 80 per cent, of its normal amount of hemo- 

 globin. The following modification of this method has been suggested by Hal- 

 dane.2 In tube A is placed a 1 per cent, solution of blood saturated with carbon 

 monoxid. Having dropped 20 cu. mm. of blood plus a slight amount of distilled 

 water into tube B, the hemoglobin contained in it is quickly converted into carbon 

 monoxid hemoglobin by charging it with pure carbon monoxid or by passing a 

 mixture containing this gas through it. The dilution of the sample of blood is 

 then accomplished in the manner described previously. Sahli^ employs a solution 

 of hematin chlorid and first converts the blood to be tested into hematin chlorid. 



SPECTROSCOPIC ANALYSIS OF HEMOGLOBIN AND ITS DERIVATIVE 



COMPOUNDS 



The most essential part of the spectroscope is a glass prism P, 

 which receives a bundle of white light through tube A (Fig. 107). 

 The size of this bundle may be varied by altering the size of the slit- 

 like opening in the end of this tube, while a biconvex lens interposed in 

 this place serves to render the rays parallel and to concentrate them 

 upon the surface of the prism at C. The spectral components of the 

 white light are observed in magnified form through tube B which is 

 nothing more than a small telescope. The third tube D contains a 

 scala M which is illuminated and reflected upon the surface of the 

 prism at C. In this way, the spectral colors (red to violet) may be 

 observed in conjunction with the divisions of the scala. 



If a colored medium, for example, a solution of hemoglobin is now 

 placed between the source of light and the opening in tube A, some of 

 the rays of white light are prevented from entering, i.e., they are ab- 

 sorbed. In consequence of this absorption, certain sections of the spec- 

 trum as observed through tube B, appear in different shades of black. 

 These dark bands situated in between the different colors, are com- 

 monly called absorption bands. Of greatest importance, however, is 



1 The Lancet, 1878. 



2 Jour, of Physiol., xxvl, 1901, 497. 



3 Lehrbuch der klin. Untersuchungsmeth., 1905. 



