238 HEMOGLOBIN. 



showed (1) that the absorption of oxygen and carbonic oxide by blood does 

 not proceed according to Dal ton and Henry's law a proof, amongst many 

 others, that these gases are chemically combined with some constituent of 

 the blood and not held in a state of simple solution ; (2) that blood which 

 has been deprived of its gases by boiling in vacuo, combines with the same 

 volume of carbonic oxide as of oxygen in other words, that when carbonic 

 oxide replaces the oxygen of the blood, one molecule of the former takes the 

 place of one molecule of the latter (i.e. CO replaces 2 ). Lothar Meyer 

 further showed that hsematin could not be the body with which 2 and CO 

 entered into combination, and expressed the surmise that it might prove 

 to be the same as constituted the red blood crystals described by Lehmann. 1 

 The truth of the surmise was soon proved beyond the possibility of doubt, 

 it being shown that the O 2 - and CO-compounds of the blood-colouring matter 

 are isomorphous, that they are characterised by a similarity in their power of 

 absorbing light, but that the CO-compound is distinguished by not being 

 decomposed by reducing agents (Hoppe-Seyler). 



Hermann 2 subsequently showed that just as CO possesses the power 

 of displacing the oxygen of oxyhaemoglobin, nitric oxide (NO) in its 

 turn is capable of displacing CO, one molecule of the former replacing 

 one molecule of the latter, the NO-compound being, like the CO-com- 

 pound, absolutely irreducible. 



The three compounds of haemoglobin were shown to be isomorphous, 

 to be characterised by a highly florid colour, only slightly differing in 

 tint one from the other; their visible spectrum was found to be distin- 

 guished by two absorption-bands between D and E, at first sight appear- 

 ing identical in the three cases, though careful measurement revealed a 

 very slight shifting of the bands towards the more refrangible end of the 

 spectrum in the case of the CO -compound. 



They were all three found to be free from pleochromatism 

 a character in which they differ strikingly from reduced haemo- 

 globin. Whilst the CO - compound is much more stable than the 

 2 -compound, the NO-compound is again more stable than the CO- 

 compound. 



It was at first believed that the CO-compound, unlike oxyhaemo- 

 globin, could not be dissociated. I was the first to show that by the 

 long-continued passage of neutral gases through solutions of CO-hsemo- 

 globin, the CO is gradually driven out, and reduced haemoglobin is 

 obtained. 3 Donders, 4 to whom the discovery of the fact is always 

 ascribed, drew attention to it in a highly interesting theoretical paper. 

 Zuntz 5 immediately afterwards showed, in contradiction of Nawrocki, 6 

 that blood saturated with carbonic oxide, when boiled in vacuo, gives up 

 its carbonic oxide and that it manifests the absorption-band of reduced 



1 " Consideranti enim quaj his in rebus din versatus Lehmann de rubris illis sanguinis 

 crystallis nuper publicavit, plus quam verisimile videbitur, hac cum substantia et oxygenium 

 et oxydum carbonicum conjunctionem chymicam posse mire"; Lothar Meyer, "De 

 sanguine oxydo carbonico infecto," p. 12. 



2 " Ueber die Wirkungen des Stickstoffoxydgases auf das Brut," Arch. f. Physiol., 

 Leipzig, 1865, S. 469. 



3 A. Gamgee, "On Poisoning by Carbonic Oxide Gas, and by Charcoal Fumes," 

 Journ. Anat. andPhysiol., London, 1867, vol. i. pp. 339-346. 



4 Donders, " Der Chemismtis der Athmung, ein Dissociations-process," Arch. f. d. ges. 

 PkysioL, Bonn, 1872, Bd. v. S. 20-26. 



5 " 1st Kohlenoxydhamoglobin eine feste Verbindung ? " Arch. f. d. ges. Physiol., 

 Bonn, 1872, Bd. v. S. 584-588. 



6 " De Claudii Bernard! methodo oxygenii copiam in sanguine determinandi," Inang. 

 Diss., Vratislaviw, 1863. 



