THE COLOURED BLOOD-CORPUSCLES. 33 



vigorously with air, and looking at once, the two bands 

 may be caused to reappear for a short time. Observe the 

 absorption of the light at the red and violet ends of the 

 spectrum according to the strength of the fluid. 



(c.) Dilute the solution, and observe that the single band 

 is not resolved into two bands, but gradually fades and dis- 

 appears. 



(d.) To a similar solution of oxy-haemoglobin showing 

 two well-defined bands, add Stokes's fluid, and observe the 

 single absorption band of reduced haemoglobin. Shake the 

 mixture with air and the two bands reappear. 



(e.) Use a solution of oxy-hsemoglobin where the two 

 bands can just be seen, and reduce it with either ammonium 

 sulphide or Stokes's fluid, and note that, perhaps, no absorp- 

 tion band of reduced haemoglobin is to be seen, or only the 

 faintest shadow of one. 



(/.) Compare the relative strengths of the solution of oxy- 

 hsemoglobin and reduced haemoglobin. The latter must be 

 considerably stronger to give its characteristic spectrum. 



Stokes's Fluid. Make a solution of ferrous sulphate ; to it 

 add ammonia after the previous addition of sufficient tartaric 

 acid to prevent precipitation. It is usual to add about three 

 parts by weight of tartaric acid to two of the iron salt. It should 

 be made fresh when required. 



10. III. Carbonic Oxide-Haemoglobin. Through a diluted solu- 

 tion of oxy-haemoglobin, or defibrinated blood, pass a stream of 

 carbonic oxide or coal gas until no more CO is absorbed. 

 Note the florid cherry-red colour of the blood. 



(a.) Dilute the solution in a test-tube and observe its 

 spectrum, noting that a stronger solution is required than 

 with HbO 2 to show the absorption bands. Two absorption 

 bands nearly in the same position as those of HbO 2 , but 

 very slightly nearer the violet end (Fig. 4, 3). Make a map 

 of the spectrum and bands. 



(b.) The bands are not affected by the addition of a re- 

 ducing agent e.g., ammonium sulphide or Stokes's fluid. 



3 



