2 4 o H. £M0 GL OB IN. 
(b) The photographic spectrum of CO-haemoglobin.— In Fig. 35 
are shown reproductions of the photographic spectrum of this com- 
pound, contrasted with that of the oxygen compound. The band of 
Soret is just as well marked in the one as in the other, but in the 
case of the CO-haemoglobin there is a decided shifting of the band 
in the extreme violet towards the red, which is somewhat curious, 
considering that the bands in the visible spectrum are, though to a 
much less extent, shifted in the opposite direction. I have shown that 
there is absolute identity in the position of the absorption-band in the 
extreme violet, in the case of the CO- and XO- c< impounds « if haemoglobin. 1 
The principal characteristic reactions of CO-haemoglobin. 
1. AVhen treated with Stokes' reagent, solutions of ammonium sulphide, 
and the like, no change whatever occurs, either in the colour or the 
spectrum of blood saturated with carbonic oxide, or in solutions of 
pure CO-haemoglobin. 
G HK L M N 
Fig. 35. — The photographic spectrum of oxyhemoglobin and of CO-lnemoglobin. 
2. The blood of men or animals asphyxiated by carbonic oxide, or 
by a gas containing it (charcoal fumes, coal gas), if pretty fully saturated, 
possesses and retains for a long time a florid arterial colour, and when 
diluted is found to be partially or completely irreducible. Hoppe- 
Seyler found that if such blood is sealed in glass tubes, it may retain for 
some years its characteristic spectroscopic properties, and even admit 
of CO being boiled out, with the aid of the mercurial pump, and 
identified by chemical analysis. 
3. The addition of a concentrated solution of sodium hydrate (density 
1*3) to blood, saturated with CO in the proportion of about two parts 
of the former to one of the latter, causes the blood to assume a tine 
scarlet colour, and to deposit a cinnabar-red precipitate. The same 
coloration and precipitate is produced with solutions of pure CO- 
haemoglobin. According to Hoppe-Seyler, the precipitate is composed 
of CO-haemoglobin, rapidly passing into CO-haemochromogen. When 
normal blood is treated in the same way with sodium hydrate, it is 
1 Gamgee, Proc. Roy. Soc. London, 1896, vol. lix. p. 276. 
