242 HEMOGLOBIN. 



to no change in the physical characters of the blood, of which the spectrum 

 remains unchanged, and of which the property of being reduced by suitable 

 agents remains unaffected. 



Upon what appears to me to be altogether insufficient evidence, Hoppe- 

 Seyler, 1 however, came to the conclusion that hydrocyanic acid forms an easily 

 decomposed compound with haemoglobin. If hydrocyanic acid be added to 

 a solution of oxyhaemoglobin, on crystallising out the latter it retains some of 

 the acid. These crystals may be repeatedly crystallised, and when dried in 

 vacuo over sulphuric acid they are found to contain hydrocyanic acid. The 

 supposed compound of hydrocyanic acid with oxyhaemoglobin presents an 

 absorption-spectrum absolutely identical with that of oxyhaemoglobin, and is 

 reduced just as easily by such agents as ammonium sulphide or Stokes's re- 

 agent. On the other hand, blood to which hydrocyanic acid has been added 

 shows the bands of oxyhaemoglobin for a much longer time than normal blood. 



It appears to me that no proof whatever has been advanced of the 

 existence of a chemical compound of oxyhaemoglobin with HCN. 



That some hydrocyanic acid should adhere to haemoglobin, as it crystallises 

 out of the mother liquor which contains the acid, is quite in accordance with 

 a number of experiences of a similar kind, and can by itself afford no evidence 

 of an actual compound existing. The resistance of blood to which hydro- 

 cyanic acid has been added, to decomposition, when confined in a sealed or 

 closed vessel, can, on the other hand, be easily explained by the unquestion- 

 able arrest or slowing of the process of putrefaction in the presence of hydro- 

 cyanic acid. It is, undoubtedly, the products of putrefaction which are the 

 causes of the apparently spontaneous reduction of the oxyhaemoglobin of blood 

 confined in a receptacle to which air has no access ; so that an agent which 

 does inhibit putrefaction as hydrocyanic acid unquestionably and admittedly 

 does and, at the same time, does not, at ordinary temperatures, decompose 

 oxyhaemoglobin, would be expected to act as hydrocyanic acid has been found 

 to do in furthering the persistence of the oxyhaemoglobin bands. 



What I have just stated in reference to the probable non-existence of a 

 compound of HCN with oxyhaemoglobin, does not imply my disbelief in the 

 existence of an interesting compound of hydrocyanic acid with methaemo- 

 globin, described by Robert, which will be discussed after the latter body 

 has been described. 



2. With cyanogen. Kay Lankester' 2 believed that cyanogen formed a 

 compound with haemoglobin, probably analogous to the CO- and NO-com- 

 pounds, and characterised by an absorption-band, resembling that of, but 

 obviously not due to, reduced haemoglobin. Many discordant statements have 

 been published on this matter. It appears that by the prolonged action of 

 cyanogen, as by the prolonged action of HCN, there is produced Kobert's 

 cyanogenmethaemoglobin (see p. 248). 



3. With acetylene (C 2 H 2 ). Bistrow and Liebreich 3 surmised that acety- 

 lene forms a very unstable compound with haemoglobin, easily reducible by 

 sulphide of ammonium and similar agents. On the evidence at present at our 

 disposal, the existence of this compound must be considered as more than 

 problematical. 



4. With carbon dioxide. According to Bohr, haemoglobin forms a series 

 of compounds with carbon dioxide, which possess spectra identical with those 

 of reduced haemoglobin. He states, further, that if a solution of haemoglobin 

 be brought in contact with a mixture of oxygen and carbon dioxide, the 



1 " Cyanwasserstoffheemoglobinverbindungen," Med.-chem. Untcrsuch., Berlin, 1868, S. 

 206-208. 



2 " Ueber den Einfluss des Cyangases auf Hamoglobin nach spectroscopischen Beobach- 

 tungen," Arch. f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 491-493. 



8 " Ueber die Wirkung des Acetylens auf das Blut," Ber. d. deutsch. chem. Gesellsch., 

 Berlin, 1868, Bd. i. S. 220. 



