MICROSCOPIC STRUCTURE OF THE BLOOD. 



285 



For studying the visible spectrum of hemoglobin, Gamgee 

 recommends a spectroscope of the ordinary Bunsen type, provided 

 with a single good flint-glass prism, or direct vision spectroscopes 

 of the Browning or Hofmann patterns. If minute quantities of 

 coloring-matter are to be investigated, microspectroscopes may be 

 used i. e., direct vision spectroscopes adapted to the eye-piece of 

 a compound microscope. As the source of light, he recommends 

 a gas lamp, furnished with the Auer incandescent burner. 



It is convenient to have the solutions, whose absorption-spectra 

 are to be examined, in cells with perfectly parallel sides, and a defi- 

 nite width apart; such an apparatus is the hematinometer (Fig. 153). 



The hematoscope or hemoscope of Hermann (Fig. 154) is also 

 used for this purpose. In this apparatus the thickness of a layer 

 of fluid can be regulated by sliding c toward F, and measured by 

 a scale on c. F and c are glass plates through which and the 

 intervening fluid light is transmitted for spectroscopic examina- 

 tion. 



Spectrum of Oxyhemoglobin (Fig. 155). Dilute solutions of 



70 65 



6O 



55 



50 



4-5 



B C 



E b 



FIG. 155. Diagrammatic representation of the absorption-spectrum of oxyhemo- 

 globin. The numerals give the wave-lengths in hundred-thousandths of a milli- 

 meter ; the letters show the positions of the more prominent Fraunhofer lines of the 

 solar spectrum. The red end of the spectrum is to the left. The a-band is to the 

 right of D, the 0-band to the left of E (after Eollett). 



oxyhemoglobin give two absorption-bands between D and E. The 

 band nearer D i. e., the red end of the spectrum is known as the 

 " a-band "; the one near E is the " /3-band," and is broader, lighter, 

 and less clearly defined than the a-band. The center of the 

 a-band corresponds to a wave-length of 579 millionths of a milli- 

 meter (/I 579) ; while the center of the /9-band corresponds to 

 X 553.8. 



Spectrum of Hemoglobin (Reduced Hemoglobin) (Fig. 156). 

 Oxyhemoglobin may be reduced to hemoglobin by adding to its 

 solutions Stokes' reagent, which is made by dissolving 2 parts by 

 weight of ferrous sulphate, adding 3 parts of tartaric acid, and 

 then adding ammonia until the reaction is distinctly alkaline. 

 When thus reduced the a- and /9-bands disappear, and the " /-band " 

 appears ; this is a single band between D and E, its darkest part 

 being nearer D than E, and corresponding to about ^ 550. If the 

 solution is shaken with air, the appearance of the a- and /9-bands 

 shows that oxyhemoglobin has been formed. 



