236 HEMOGLOBIN. 
chamber connected with the mercurial pump, some of the oxygen must be used 
up in oxidising the readily oxidisable substances existing in the blood, and 
especially in venous blood, and an error will be thereby introduced unequally 
affecting different samples of blood, — an error which is influenced by the 
duration and extent to which the heat is applied to the blood and the rapidity 
with which the aqueous vapour and gases evolved by the blood are removed. 
The photographic spectrum of reduced haemoglobin. — When 
the molecule of dissociable oxygen is removed from oxyhemoglobin, 
either by the action of reducing agents, or by boiling in vacuo, the 
absorption-band in the extreme violet is remarkably displaced towards 
the less refrangible end of the spectrum, the centre of absorption 
corresponding to a 426-0. The difference in the position of Soret's 
band in the oxy- and in reduced luemoglobin is shown in the photo- 
type (Fig. 33). When we reflect that the addition of a molecule of 
oxygen to the enormous molecule of hemoglobin cannot affect in an 
appreciable manner the mass of the molecule, we must conclude that 
the displacement of the absorption-band towards the ultra-violet end 
when haemoglobin combines with oxygen (all other conditions remaining 
the same), indicates that this combination leads to a notable acceleration 
of the motion of the intramolecular group of carbon atoms upon which 
the extreme violet absorption-band depends. 
The amount of oxygen with ■which haemoglobin combines to 
form oxyhaemoglobin. — It is believed, on various grounds, that one 
molecule of hemoglobin combines with one molecule of oxygen to form 
the compound which we know as oxyhemoglobin. 
The most recent determinations made by Hiifner have shown that 
1 grm. of reduced hemoglobin of the ox can link to itself 1*338 c.c, of 
oxygen or carbonic oxide (measured at 0° C. and 760 mm. pressure). 
The molecular weight of the hemoglobin of the ox (calculated from 
Hiifner's most recent estimations of the iron wdiich this body contains) 
= 16669. The volume of oxvgen absorbed by reduced haemoglobin, 
calculated from this molecular weight, should be 1*34 c.c, so that the 
result of experiment agrees in a surprising manner with theory. 
Differences in chemical reactions between solutions of reduced 
and oxyhaemoglobin. — 1. Solutions of reduced hemoglobin when boiled 
in vacuo, or subjected to the action of CO, unlike solutions of oxyhemo- 
globin, yield no oxygen. 
2. They are not decomposed even by long contact with trypsin, which 
readily splits up oxyhaemoglobin into hematin and the products of 
trypsin proteolysis. 
3. They are unaffected by H 2 S, wdiich, when acting for a sufficient 
length of time upon oxyhemoglobin, converts it into sulpho-methemo- 
globin. 
4. Nitrites, potassium ferricyanide, and permanganate, and many 
other oxidising and reducing agents, exert no action on reduced hemo- 
globin, whilst they convert oxyhemoglobin into methemoglobin. 
5. "When treated with alcoholic or watery solutions of acids or 
alkalies, in the complete absence of free oxygen, haemoglobin yields 
purple-red solutions or precipitates. The hemoglobin is, under these 
circumstances, split up into an iron-containing coloured body — luvmo- 
chromogcn — and into an albuminous body or bodies. Oxyhemoglobin, 
under the same conditions, splits up into an iron-containing body — 
harmatin — and albuminous products. 
