224 ELEMENTARY PHYSIOLOGY. [XXI. 



also is absorbed, and only the red is visible, 

 and this at last disappears. 



C. Reduce the oxy haemoglobin solution with Stokes's 

 reducing 1 fluid in the cold, or with a few drops of 

 ammonium sulphide solution warming gently. 



a. Compare the claret colour of the reduced 

 haemoglobin solution with the bright scar- 

 let of the original solution. 



b. Examine with the spectroscope. There is a 

 single broad band, occupying a position in- 

 termediate between those of the two oxy- 

 haemoglobin bands which have disappeared. 

 The band is not quite intermediate ; its mid- 

 line (w. L. about 565) lies nearer D than E. 

 This single band is much less dark than 

 either of the two bands produced by the 

 same quantity of oxyhsemoglobin. 



c. With stronger solutions less of the blue of 

 the spectrum and more of the red (between 

 C and D) is absorbed than with a solution of 

 oxyhaemoglobin. 



7. Shake well the reduced solution, pour it two or 

 three times from one vessel into another so as to 

 expose it thoroughly to air; and examine it at 

 once. The bright scarlet colour will be restored; 

 the oxyhsemoglobin spectrum will reappear. 

 If allowed to remain at rest, reduction, from 

 excess of reducing reagent present, may soon 

 return. 



1 See Appendix. 



