340 



AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



(583 raillionths of a millimeter) and A 571, and the /?-band between ^ 550 and 

 X 532 (Gamgee). The width and distinctness of the bands vary naturally 

 with the concentration of the solution used (see PI. I. spectra 2, 3, 4, and 5), 



70 65 



6O 



55 



50 



B C 



D 



Q 



-0.9 



BHI 0.8 



-0.7 



0.5 



0.4 



0.3 



0.2 



m o. i 



FIG. 88. Diagrammatic representation of the absorption spectrum of oxyhsemoglobin (after Rollett). 

 The numerals give the wave-lengths in hundred-thousandths of a millimeter ; 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-baiid is to the right of D, the /3-band to the left of E. 



or, if the concentration remains the same, with the width of the stratum of 

 liquid through which the light passes. With a certain minimal percentage of 



oxyhsemoglobin (less than 0.01 per 

 cent.) the /9-band is lost and the - 

 band is very faint in layers one cen- 

 timeter thick. With stronger solu- 

 tions the bands become darker and 

 wider and finally fuse, while some 

 o..e of the extreme red end and a great 

 deal of the violet end of the spec- 

 trum is also absorbed. The varia- 

 tions in the absorption spectrum with 

 differences in concentration are clear- 

 ly shown in the accompanying illus- 

 tration from Rollett l (Fig. 89) ; the 

 thickness of the layer of liquid is 

 supposed to be one centimeter. The 

 numbers on the right indicate the 

 percentage strength of the oxy- 

 hsemoglobin solutions. It will be 

 noticed that the absorption which 

 takes place as the concentration of 

 the solution increases affects the red- 

 orange end of the spectrum last of all. 

 Solutions of reduced haemo- 

 globin examined with the spectro- 

 scope show only one absorption 

 band, known sometimes as the 

 "y-band." This band lies also in 

 the portion of the spectrum included 

 between the lines D and E; its relations to these lines and the bands of 

 oxyhaemoglobin are shown in Figure 90 and in PI. I. spectrum 6. The 

 1 Hermann's Handbuch der Physiologic, vol. iv., 1880. 



0, 



aBC 



G 



ft 



FIG. 89. Diagram to show the variations in the ab- 

 sorption spectrum of oxyhsemoglobin with varying 

 concentrations of the solution (after Rollett). The 

 numbers to the right give the strength of the oxy- 

 hsemoglobin solution in percentages ; the letters give 

 the positions of the Fraunhofer lines. To ascertain 

 the amount of absorption for any given concentration 

 up to 1 per cent., draw a horizontal line across the 

 diagram at the level corresponding to the concentra- 

 tion. Where this line passes through the shaded part 

 of the diagram absorption takes place, and the width 

 of the absorption bands is seen at once. The diagram 

 shows clearly that the amount of absorption increases 

 as the solutions become more concentrated, especially 

 the absorption of the blue end of the spectrum. It 

 will be noticed that with concentrations between 0.6 

 and 0.7 per cent, the two bands between D and E fuse 

 into one. 



