HEMOGLOBIN (REDUCED HEMOGLOBIN}. 229 



HEMOGLOBIN (EEDUCED HEMOGLOBIN). 

 SYNONYM, "PURPLE CRUORIN." 



Historical note. Fully two years had passed since the date of Hoppe's 

 publication (1862) of his observations on the spectrum of blood, before it was 

 shown that the oxygen which enters into combination with haemoglobin has 

 a fundamental influence on its spectrum. It was on the 16th of June 1864 

 that Professor Stokes 1 communicated to the Royal Society the interesting 

 observation that when diluted blood is treated with certain reducing agents, 

 the colour of the liquid and its spectrum undergo remarkable changes ; the 

 former loses its bright red appearance, becoming darker in tint, whilst the 

 absorption-bands a and /3 are replaced by a single band which we may 

 designate the band y, which appears less deeply shaded and with less denned 

 edges, and which extends from D nearly to E. If, now, the solution which 

 exhibits this spectrum be shaken with air or oxygen, the single band at 

 once gives place to the two original bands, whilst the liquid reacquires 

 more or less of its primitive florid-red colour. The process of reduction 

 and oxidation may be repeated many times in succession. 



From his experiments, Stokes concluded that "the colouring matter of blood, 

 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 oxidised state by the action of 

 suitable reducing agents, and recovers its oxygen by absorption from the air." 2 



The researches of Magnus, Lothar Meyer, and Claude Bernard had shown 

 that the blood holds in solution an amount of oxygen greatly in excess of that 

 which could exist in a state of simple solution, but that this oxygen exists in a 

 condition which permits of its being extracted from the blood by boiling in a 

 Toricellian vacuum, as well as by the action of carbonic oxide. Hoppe-Seyler, 

 having succeeded in crystallising oxyhsemoglobin, and, by means of its optical 

 properties, having identified it with the colouring matter as it exists in the living 

 blood, was able to show that a solution of crystallised oxyhsemoglobin behaves 

 towards reducing solutions in the same manner as diluted blood; that, like blood, 

 it yields oxygen when boiled in vacuo, and that the blood-colouring matter thus 

 deprived in vacuo of its loosely combined or respiratory oxygen manifests the 

 absorption-band which had been described by Stokes as the result of reduction. 



The further steps in the growth of our knowledge of reduced haemoglobin 

 will be more conveniently referred to in discussing the chief facts with which 

 we are acquainted relative to this remarkable body. 



Methods of effecting the reduction of oxyhsemoglobin to reduced 

 haemoglobin. In nearly all experiments on the reduction of oxyhsemo- 

 globin, diluted blood may be substituted for a solution of the pure blood- 

 colouring matter, it having been shown by the spectrophotometric and 

 chemical researches of Hiifner that, both in respect of their power of 

 absorbing light and of the influence of reducing agencies upon them, the 

 two solutions possess identical properties. Instead, however, of employ- 

 ing pure distilled water as a diluent, it is advisable to use, according to 

 Hiifner 's plan, a 01 per cent, solution of sodium hydrate. A diluted 

 solution of blood prepared in this way is free from all turbidity, and 

 therefore more transparent than a pure aqueous solution, and undergoes 

 putrefactive alterations more slowly. 



1 l( On the Reduction and Oxidation of the Colouring Matter of the Blood," Proc. Roy. 

 Soc. London, 1864, vol. xiii. pp. 353-364 ; London, Edinburgh, and Dublin Phil. Mag., 

 London, 1864, vol. xxviii. pp. 391-400. 



2 Stokes, op. cit., p. 357, par. 8. 



