242 HAEMOGLOBIN. 
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 oxyhemoglobin, 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 oxyhemoglobin presents an 
absorption-spectrum absolutely identical with that of oxyhemoglobin, 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 oxyhemoglobin 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 oxyhemoglobin with HCX. 
That some hydrocyanic acid should adhere to hemoglobin, 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 
dosed 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 oxyhemoglobin 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 
oxyhemoglobin, would be expected to act as hydrocyanic acid has been found 
to do in furthering the persistence of the oxyhemoglobin bands. 
What I have just stated in reference to the probable non-existence of a 
compound of HCN with oxyhemoglobin, does not imply my disbelief in the 
existence of an interesting compound of hydrocyanic acid with methemo- 
globin, described by Kobert, which will be discussed after the latter body 
has been described. 
2. With cyanogen. — Kay Lankester 2 believed that cyanogen formed a 
compound with hemoglobin, probably analogous to the CO- and NO-coni- 
pounds, and characterised by an absorption-band, resembling that of, but 
obviously not due to, reduced hemoglobin. Many discordant statements have 
been published on this matter. It appears that by the prolonged action of 
cyanogen, as by the prolonged action of HCX, there is produced Robert's 
cyanogenmethemoglobin (see p. 248). 
3. With acetylene (C 2 H 2 ). — Bistrow and Liebreich 3 surmised that acety- 
lene forms a very unstable compound with hemoglobin, 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, hemoglobin forms a series 
of compounds with carbon dioxide, which possess spectra identical with those 
of reduced hemoglobin. He states, further, that if a solution of hemoglobin 
be brought in contact with a mixture of oxygen and carbon dioxide, the 
1 " Cyanwasserstofflicemoglobinverbindiirigen," Med.-cliem. Untersuch., Berlin, 1868, S. 
206-203. 
2 " Ueber den Einfluss des Cyangases auf Haruoglobin nacb spectroscopischen Beobacli- 
tungeu," Arch./, 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. 
