100 HAEMOGLOBIN OR REDUCED HAEMOGLOBIN. [BOOK I. 



had existed between the absorption bands a and $ of oxy-haemo- 

 globin disappears, and instead of the two bands there appears a 

 single one, less deeply shaded and with less finely denned edges, 

 extending between D and E. This band we may -distinguish as 

 absorption band 7. (See Fig. 22, Spect. 5 for description.) 



Hoppe-Seyler 1 , who has described the spectrum of reduced haemo- 

 globin with great care, remarks that when a strong solution of that body 

 is diluted with water, avoiding at the same time the access of oxygen, 

 before the distinct absorption band which we designate 7 comes into 

 distinctness there is seen some green light between b and F. As the 

 solution is diluted, the dark absorption band, which extends at first 

 from D to b, diminishes in width, and the blue rays of the spectrum 

 become more distinctly visible. 



On further diluting, the single absorption band is observed not to 

 exhibit any trace of subdivision, but to dimmish rapidly in intensity, 

 so that in a solution of such concentration that both absorption 

 bands of oxy-haemoglobin would be quite distinct, the single band 7 of 

 reduced haemoglobin has disappeared from view. Further, reduced 

 haemoglobin existing in solution is distinguished from oxy-haemo- 

 globin by its stronger absorption of the light between C and D, as 

 well as by its weaker absorption of the blue light above F. 



If now the solution which presents this spectrum be shaken 

 with air or oxygen, the single band at once gives place to the two 

 original bands, whilst the liquid loses its brown and reacquires more or 

 less of its florid red colour. The process of reduction and subsequent 

 oxygenation may be repeated many times in succession. 



From his experiments Stokes concluded that "the colouring matter 

 of bloody like indigo, is capable of existing in two states of oxidation, 

 distinguishable by a difference of colour and a fundamental difference 

 in the action on the spectrum. It may be made to pass from the more 

 to the less oxidized state by the action of suitable reducing agents, and 

 recovers its oxygen by absorption from the air*." This surmise has 

 been proved to have been perfectly correct, and to blood- colouring 

 matter after it has lost the oxygen which it can give up to reducing 

 agents, the name of reduced haemoglobin is given. By many, as by 

 Hoppe-Seyler, it is termed simply haemoglobin, to distinguish it from 

 the body as it exists combined with its respiratory oxygen and which 

 is then termed oxy-haemoglobin. 



Methods Before proceeding further, it is advisable to consider 



of reducing j low fa Q blood or a solution of ^xy-haemoglobin may be 



gio^ixrto'bae- reduced so as to exhibit the spectrum of haemoglobin, 

 moglobin. The following are the methods which may be followed : 



1 Hoppe-Seyler, "Beitrage zur Kenntniss des Blutes des Menschen und der 

 Wirbelthiere. Das reducirte Hamoglobin oder der venose Blutfarbstoff." Med. Ghem. 

 Untersuchungcn, Heft in. (1868) at p. 374 et seq. 



2 Stokes, "On the reduction and oxidation of the colouring matter of the blood," 

 by Professor Stokes, F.E.S. Proceedings of the Royal Society of London, Vol. xm. 

 (1864) p. 357, paragraph 8. Also Philosophical Magazine, 1864, p. 391. 



