42 



AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



(583 millionths of a millimeter) and / 571, and the ,9-band between X 550 and 

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

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



70 65 



55 



B C 







It 



E b 



F 



G 



Fig. 3.— Diagrammatic representation of the absorption spectrum of oxyhemoglobin (after Rollett). 

 The numerals give the wave-lengths in hundred-thousandths of a millimeter; the letters Bhow 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 /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 



oxyhemoglobin (less than 0.01 per 

 cent.) the /3-band is lost and the a- 

 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 

 of the extreme red end and a great 

 deal of the violet end of the spec- 

 trum is also absorbed. The varia- 

 tions in theabsorption spectrum with 

 differences in concentration are clear- 

 ly shown in the accompanying illus- 

 tration from Rollett 1 (Fig. 4) ; 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- 

 hemoglobin solutions. It \vill be 

 noticed that the absorption which 

 takes place as the concentration of 

 the solution increases affects the fed- 

 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 i> and K; its relations to these lines and the bands of 

 oxyhemoglobin are shown in Figure 5 and in PI. I. spectrum 6. The 

 1 Hermann's Handbuchder Pkysiologie, Bd. iv., 1880. 



Fig. 4. — Diagram to show the variations in the ab- 

 sorption spectrum of oxyhemoglobin with varying 

 concentrations of the solution (after Rollett). The 

 numbers to the right give the strength "f the oxy- 

 globin solution in percentages; the lettersgive 

 th<> positions of the Fraunhofer lines. To ascertain 

 tin- amounl of absorption for any given concentration 

 up to l per cent., draw a horizontal line across tin' 

 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 i- seen al once. The diagram 

 .-how- clearly that the amount of absorption increases 



a- the solutions become m<>rc ncentrated, especially 



the absorption of the blue end of the spectrum. It 

 will he noticed that with concentrations between or, 

 and 0.7 per cent, the two bands between Dandi fuse 

 into ' 



