THE BLOOD 



249 



Dilute solutions of arterial blood show absorption bands between the 

 Fraunhofer lines, D and E, in the green and yellow portion of the spectrum. 



FIG. 102. THE SPECTROSCOPE. A. Telescope. B. Tube for the admission of light and 

 carrying the collimator. C. Tube containing a scale, the image of which when illuminated is 

 reflected above the spectrum. D. The fluid examined. (Landois and Stirling.) 



(See Fig. 103.) The band nearest D, frequently designated as alpha, is dark 

 in the center and sharply denned. The band which lies toward E, desig- 

 nated as beta, is broader and less sharply defined. 



Yellow. 



Green. 



Cyan Blue. 



70 



E b 



100 no 



Oxy 



hemoglobin 

 0.8 %. 



FIG. 103. SPECTRA OF HEMOGLOBIN AND SOME OF ITS COMPOUNDS. 

 (Landois and Stirling.) 



As the amount of light absorbed varies with the concentration ^ of the 

 solution as well as its thickness, and gives rise to absorption bands of different 



