250 



TEXT-BOOK OF PHYSIOLOGY 



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

 nated as beta, is broader and less sharply denned. 



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 

 widths and intensities, it becomes necessary, in order to obtain the character- 

 istic bands, to employ only dilute solutions. 



The absorption spectra, as seen with different strengths of solution one 

 centimeter thick, are shown graphically in Fig. 102. It will be observed 

 that solutions varying in strength from o.i per cent, to 0.6 per cent, give rise 

 to the two characteristic bands, but with gradually increasing breadths. 

 With a percentage greater than 0.65 per cent, the light between D and E, 

 the yellow-green, becomes extinguished and .the two bands fuse together, 

 forming a single band overlapping slightly the lines D and E. At the same 

 time there is a progressive darkening of the violet end of the spectrum. At 

 0.85 per cent., all the light is absorbed with the exception of a small amount 



aBC D Eb F G h 



FIG. 102. GRAPHIC REPRESENTA- 

 TION OF THE ABSORPTION OF LIGHT IN 

 A SPECTRUM BY SOLUTIONS OF OXY- 

 HEMOGLOBIN OF DIFFERENT STRENGTHS. 

 The shading indicates the amount of 

 absorption of the spectrum, and the 

 numbers at the side the strength of the 

 solution. (Rottet.} 



a3C D Eb F G h 



FIG. 103. GRAPHIC REPRESENTATION 

 OF THE ABSORPTION OF LIGHT IN A SPEC- 

 TRUM BY SOLUTIONS OF REDUCED HEMO- 

 GLOBIN OF DIFFERENT STRENGTHS. The 

 shading indicates the amount of absorp- 

 tion of the spectrum, and the numbers at 

 the side the strength of the solution. 

 (Rollet.) 



of the red. Solutions less than o.oi per cent, to 0.003 P er cen t- show but a 

 single absorption band that nearest D. 



A solution of venous blood or of reduced hemoglobin shows but a single 

 absorption band (see Fig. 101), frequently designated as gamma, broader 

 and less marked between the lines D and E, but extending slightly beyond D. 

 Fig. 103 shows in the same graphic manner the increasing breadth of the 

 absorption band with increasing strengths of solution, as well as the simul- 

 taneous absorption of light at both the red and violet ends of the spectrum. 



Oxyhemoglobin ; Reduced Hemoglobin. The coloring-matter of 

 the blood is characterized by the property of combining with and of again 

 yielding up oxygen. The union is a chemic one, taking place under certain 

 pressure conditions. It therefore may exist in two states of oxidation, 

 distinguished by a difference in color and their absorption spectra. If 

 hemoglobin either in blood or in solution be shaken with air, it at once 

 combines with oxygen and is converted into oxyhemoglobin, which imparts 

 to the blood or solution a bright red or scarlet color. If the blood or solu- 



