176 
J. CAMPBELL. 
ulcer or sore has become established. It has been very thor¬ 
oughly demonstrated that by regular and uniform pressure all 
the blood can be forced out of a limb so that a perfectly blood¬ 
less operation can be made ; on the same principle, the indura¬ 
ted mass surrounding the ulcer or sore exerts a uniform pressure 
on the circulation and impedes or retards it. We believe all 
surgeons will admit this statement to be a fact. Suppose, there¬ 
fore, for the sake of argument, that this impediment to the 
circulation amounts to 20 per cent., what is the result at the 
ulcer? 
The 4-5 of the normal supply circulating through the indura¬ 
ted mass is required to give up as much oxygen to the tissue for 
its support as would be required from a full supply ; again, the 
amount of carbon dioxide taken up by the reduced circulation 
is the same as would be given up to a full circulation ; hence, 
when the blood reaches the ulcer, the proportions of oxygen to 
carbon dioxide are very materially changed ; instead of being 
one to four—the normal amount found in venous blood—we 
have a proportion of one to five or more. If one to four be 
about the limit at which tissue can be repaired, it then becomes 
very evident why a condition of that kind will not heal, and 
our course of treatment in order to be successful is also very 
plain. 
If such a condition is brought about and maintained from a 
lack of oxygen circulating in that particular part, and if a cer¬ 
tain per cent, of oxygen in the blood is absolutely necessary to 
the work of reparation, then it becomes evident that the only 
rational course we can intelligently pursue is to supply the 
want. The above proposition has been clearly and conclusively 
proven during the past 80 years, when Drs. Hill, Thornton, and 
Cavallo made their experiments on oxygen as a therapeutic 
agent, beside very many others of repute since that time; but 
as all of those men were obliged to use it in the form of a gas, 
we understand why it did not come into general use. For many 
years the attention of many of the brightest minds the world 
has produced has been directed to the question of obtaining 
