VII.] 



WAVE-LENGTHS. 



57 



globin solution with Stokes's fluid — noticing the change of the 

 colour to that of purplish or claret — until a solution is obtained 

 which gives the single characteristic absorption-band of reduced 

 Hb. Tliis is usually obtained with a solution of Hb of about 0.2 

 per cent. 



(b.) Observe the single absorption-band less deeply shaded, and 

 with less defined edges between D and E, conveniently designated 

 by the letter a. It extends between W.L. 595 and 538, and is 

 not quite intermediate between D and E ; is blackest opposite 

 W.L. 550, so that it lies nearer D than E. Both ends of the 

 spectrum are more absorbed than with a solution of oxy-haemo- 

 globin of the same strength. On further dilution of the solution, 

 the band does not resolve itself into two bands, but simply 

 diminishes in width and intensity (fig. 32, 5). 



FlQ. 32.— The Spectra of Oxy-Haemoglobin (i, 2, 3, 4), 1=0.1, 2=0.2, 3 = . 37, 4 = . 8 per cent, 

 of Oxy-Haemoglobiu, Hjemoglobin (5), and Carbonic Oxide Haemoglobin (6). Wave- 

 lengths added. The numbers attached to the scale indicate wave-lengths expressed 

 in loo.oooths of a millimetre. 



3. W.L. of the Spectrum of Carbonic Oxide Hasmoglobin. 



(a.) Use a dilute solution of carbonic oxide haemoglobin of such 



strength as to give the two characteristic absorption-bands. 



(h.) Observe the two bands, a and f3, like those of HbO.^, but 

 both are very slightly more towards the violet end of the spectrum. 

 a extends from about W.L. 587 to 564, and f3 from 547 to 529. 



(c.) No reduction is obtained by reducing agents (fig. 32, 6), 



