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VI. Experiments upon the Heart of the Dog with reference to the Maximum Volume of 
Blood sent out big the Left Ventricle in a Single Beat, and the Influence of 
Variations in Venous Pressure, Arterial Pressure, and Pulse-Rate upon the work 
done by the Heart. 
By Wm. H. Howell, A.B., Fellow of the Johns Hopkins University, Baltimore, 
and F. Donaldson, Jun., A.B. 
Communicated by Professor M. Foster, Sec. R.S. 
Received May 28—Read May 31, 1883. 
[Plate 7.] 
The most important factor to be determined before calculating the work done by 
the heart is the quantity of blood forced from the ventricles at each systole. Most 
of the efforts to determine this quantity have been based either upon faulty obser¬ 
vations upon the dead heart, or upon the uncertain data obtained by estimating the 
mean velocity of the stream of blood in the aorta. Professor Martin accordingly 
suggested to us that we should attempt to measure it directly on the isolated Dog’s 
heart. The work thus undertaken was carried on during the greater part of the 
university session, 1881-82, and the results obtained are given in the following pages. 
The method of isolating the heart was essentially that described in Professor Martin’s 
paper (Phil. Trans., 1883, p. 663). 
In the course of this work many unexpected difficulties arose, necessitating changes 
in the apparatus and the method of operating, and preventing us for a long time 
from obtaining any successful results. In our experiments it was necessary not only 
that the heart should live and beat, but that it should be in the best possible 
physiological condition, and any marked pulmonary oedema made an experiment 
nearly valueless. This most frequent cause of failure was mainly owing to the 
fact that, on account of the large quantity of blood required for an experiment, we 
were obliged to use Calf’s blood obtained from the butcher ; very often this blood, 
as Professor Martin states in his paper, will bring about oedema of the lungs in a 
short time ; large quantities of exuded serum pour out of the tracheal cannula, the 
air-passages in the lungs become choked up with liquid, and the circulation from 
the right to the left side of the heart is greatly impeded. We have succeeded, 
however, in making a considerable number of experiments in which all the conditions 
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