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apparatus. Of course we endeavoured to preclude errors by control- 
experiments with normal subjects and by taking due Measures. 
It proved possible to determine the amount of Hb which is con- 
verted to SHb. This determination is based on the now generally 
received conception that haemoglobin is a well-defined substance 
that contains to each molecule one atom of iron. 
In a closed vessel supplied with pure oxygen, haemoglobin takes 
up a constant amount of oxygen. The amount of iron in a given 
quantity of haemoglobin and its loosely combined oxygen in an 
environment of pure oxygen is constant: 2 atoms of O to 1 atom 
of Fe, which is expressed in volumina: 401 ce of oxygen to one 
gram of iron. The derivatives of the red blood-pigment, the methhb., 
the sulphhb., the cyanhb., the baematin are assumed not to take up 
any oxygen from a gas-mixture. If, therefore, blood that contains 
besides oxyhb., also SHb is brought into contact with an atmos- 
phere of pure oxygen and the amount of loosely combined oxygen 
and of iron is determined, the amount of the converted Hb may 
be calculated from the difference between the known ratio of Fe:O 
and of a pure OHb solution under the same conditions (401 : 1). 
Now, Barcrort’s method affords a rather simple way to perform 
an accurate gas-analysis of the blood, while the titanium method is 
quite adapted for the iron-determination in this liquid. Dr. ENGrLKrs 
used them in investigating the blood of our patient. It became evident 
that the quantity of converted Hb varied at different times, as had 
already been made out spectroscopically. 
Once we found a quantity of converted Hb of 19°/,, another 
time of 12.5 °/,. 
In these inquiries the clinician meets with an impediment in that, 
as a matter of course, he can work only with minimal quantities 
and cannot often repeat an experiment. The field of research is 
widened considerably when experimenting with animals. This 
proved possible. At the outset of our investigation when we 
had not yet succeeded in demonstrating chemically the presence 
of H,S in the serum, we have injeeted intravenously some 
of that serum into rabbits. To our great surprise we found already 
after an hour in the blood of one of these rabbits a rather large 
quantity of SHb. It was not necessary to look for the cause of this 
surprisingly rapid action of such small amounts of the serum upon 
rabbit’s blood, for on closer inspection we were still more surprised 
at detecting in the blood of some perfectly healthy, fresh rabbits a 
physiological amount of SHb which was distinetly demonstrable by 
the spectroscope. We have subsequently examined about 26 rabbits. 
