1897 - 98 .] Dr D. F. Harris on Spectroscopy of Haemoglobin. 191 
per se, because met-hsemoglobin having been once reduced, cannot 
by oxidation be reconstituted. I fully corroborate those observers 
who lay stress only upon the band in the red in neutral and acid 
solutions — the only ones clinically met with and spectroscopically 
identical. The band in the red is alone to be relied on ; and though 
it disappears upon dilution, it is stable compared wdth the two 
between D and E. In many urines, I believe, these two bands are 
really those of Hb0 2 , which pigment is present along with a certain 
amount of met-hsemoglobin ; for after keeping such urines for a day 
or two, all the bands of met-hsemoglobin become more distinct, as 
though there had been a progressive conversion of Hb0 2 into met- 
hsemoglobin. Such hints should be borne in mind before the 
serious pathological condition of met-hsemoglobinuria is diagnosed. 
From the fact that both acid hsematin and met-hsemoglobin possess 
a band in the red, these pigments may be spectroscopically confused. 
The following points distinguish them, apart, of course, from 
measuring the wave-lengths of their bands: — 
1 . In acid hsematin the band in the red is nearer the C line. 
2. It is usually the denser band of the two. 
3. It is usually the broader band ; always so in strong solutions, 
4. In acid hsematin there is almost always more yellow-green’ 
light in its spectrum. 
5. The band in the red of met-hsemoglobin disappears on re- 
duction, that of acid hsematin does not. 
6. Met-hsemoglobin “spontaneously” decomposes in time with 
reduction to HbO ; acid hsematin, being very stable, does not. 
In connection with met-hsemoglobin, it is of interest to note that 
it is the pigment present in the material obtained from cases of 
hsematemesis ; of course, quite unaltered blood may be vomited, 
but if the material be kept for some time, a band in the red will 
develop. 
I examined several cases of hsematemesis : in one I was given a 
mass of soft, jelly-like consistence, of very dark red, not “coffee- 
ground ” colour, unmixed with food. It was faintly acid, and when 
first examined showed the two bands of Hb0 2 , but on being put 
aside for 18 hours the band in the red appeared. Acid hsematin 
need never be looked for in the material from hsematemesis, since 
the acid of the gastric juice is so dilute. In confirmation of this,. 
