CHAP. II.] THE BLOOD. 113 



and of sodium hydrate without dissolving. We agree with Kiihne 

 in holding that from the action of reagents one would conclude that 

 a mixture of proteids, rather than a single proteid, results from the 

 decomposition of haemoglobin. 



Haematin. 



When blood is treated with acetic acid it soon undergoes a 

 change of colour, from red to brown, which indicates the decomposition 

 of haemoglobin and the formation of haematin. If now the mixture 

 of blood and acetic acid be shaken up with ether, the latter dissolves 

 out a colouring matter, and on allowing the mixture to rest, the 

 coloured ether may be decanted. 



On examining the ethereal solution it is seen to present the 

 spectrum represented in Fig. 23. 6, in which four separate absorption 

 bands are to be observed. Firstly an absorption band in the red between 

 C and D and corresponding to a wave-length of about 636, and secondly 

 a very faint and narrow band, close to D, with an approximate wave- 

 length of about 585, thirdly two much broader bands, one between D 

 and E, and another nearly midway between b and F, the centres of 

 which correspond approximately with wave-lengths 540 and 502 re- 

 spectively. Of all these bands the one in the red is by far the most 

 distinct. 



If instead of experimenting in this way with ether holding acid 

 haematin in solution we merely add acetic acid to a haemoglobin 

 solution, we observe that as the liquid becomes brown in colour, the 

 band in the red developes (Fig. 23. 5) ; the other absorption bauds not 

 being obvious. If we render the liquid alkaline by the addition 

 of ammonia a single absorption band is seen, but much nearer to 

 D, its centre corresponding to about 636 or 640. A marked shading 

 of the blue end of the spectrum is noticed in addition. If now a re- 

 ducing solution as of ferrous tartrate (Stokes' reagent) be added to 

 the liquid, a spectrum is obtained which is marked by two bands 

 which at first sight appear to the tyro to be identical with the bands 

 of oxy-haemoglobin, but which are distinct from these ; they will be 

 found to be nearer the blue than are the bands of 2 -Hb. (See 

 Fig. 23. 3.) 



The first spectrum described is supposed to be that of haematin 

 in acid solution, the second haematin in alkaline solution, and the 

 third that of reduced haematin (Hoppe-Seyler's Haemochromogen). 

 That the last is a less oxygenized product than the second is proved, 

 not only by the fact that it is produced by the action of reducing agents, 

 but likewise by the fact that on shaking the two-banded spectrum of 

 reduced haematin with air or oxygen the two bands disappear and 

 are replaced by the single bands of alkaline haematin. 



As will be more fully stated when discussing haemochromogen, 

 haematin is, according to Hoppe-Seyler, an oxidation product of 

 haemoglobin ; and it differs from haemochromogen, in that the latter 



G. 8 



