ON THE HEART OF THE DOG. 
151 
A curve of work constructed upon the arterial pressures as abscissas, and the work 
done at each beat of the ventricle under these pressures as ordinates, would, within the 
limits for which we have investigated it, be a straight line. Owing to the sources of 
error which we have enumerated above, the results were not sufficiently accurate to 
construct such a curve. 
III. 
Influence of venous pressure on the work done by the heart. 
In our experiments on the maximum outflow from the ventricles at each systole the 
venous pressure was varied, as stated, from 10 centims. to GO or 70 centims. The 
complete tables of four of the experiments are given below. 
In accordance wdth the results of Professor Martin’s previous work, it was found 
that variations of venous pressure from 10 centims. to even as high as 70 centims. 
have no direct effect on the pulse-rate. 
It was not possible to keep the arterial pressure constant, since at the higher venous 
pressures the left ventricle pumped out much more blood at each systole, and the 
increased outflow caused an increased tension in the outflow tubes and the roots of 
the great arteries still connected with the left ventricle. Since, however, as we have 
seen, the amount of outflow is not affected by the arterial pressure within the limits 
occurring in the experiments, we have sought to eliminate the influence of the 
variations in arterial pressure on the work done, by calculating the work for 100 
millims. arterial pressure in all cases, and placing the results in the column to the 
right of those calculated from the arterial pressures recorded ; in this way a clearer 
idea of the influence of venous pressure alone on the work done by the heart is 
obtained—the same thing is shown, of course, in the column giving the outflows at 
each beat. 
