ON THE HEART OF THE DOG. 
145 
from the left ventricle at each systole to the weight of the animal, when the heart 
is heating at 120 per minute, is about *0014, or 
It should be mentioned that care was taken in these experiments that the heart 
should receive an abundant supply of blood. The possible outflow from the flasks 
in 30 seconds for each venous pressure used was determined beforehand, and found 
to exceed by several hundred cubic centimetres the actual quantities pumped out by 
the heart. 
When we come to apply the knowledge obtained in this way from the isolated 
heart to the heart in the normal animal, we are met with the difficulty of deciding 
which of the results to take as most nearly representing the actual condition of things 
in the body. For several reasons we are inclined to believe that the maximum outflow 
comes closer to the average quantity thrown out during life at each systole than 
any other we might take; in other words we think it very probable that the left 
ventricle during life is distended during each diastole to about its maximum capacity. 
Such a supposition is supported by the work of Foy (4) on the Frog’s heart. 
Foy found for the Frog that with an intra-ventricular pressure of 15 centims., the 
capacity of the ventricle had practically reached its limit, and that this is just about 
the amount of intra-ventricular pressure during life, “ The intra-ventricular pressure 
during diastole, so far as it is governed by the auricles, will vary from 2 to 10 centims., 
precisely the limit at which the ventricle has its greatest possible distensibility 
within the limits of elasticity.” 
Another point which may be brought forward that lends some probability to this 
view, is found in a consideration of the time required for a complete circulation of the 
blood to take place. Knowing the proportion of the total weight of blood to the 
weight of the Dog, and the quantity of blood discharged from the heart at each 
systole, it is evident that we have a ready means of determining the time necessary 
for the completion of a circulation. Let us see how the time obtained by supposing 
that our maximum quantity represents the true capacity of the ventricle during 
life agrees with the results obtained from Dogs by direct experiment. 
Taking a Dog weighing 8000 grms., the total quantity of blood will be equal 
to 8000 X '076 = 608 grms. The weight of blood thrown out from the left ventricle 
at each systole, with a pulse-rate of 120, will be about 8000X'0014= 11 *2 grms. 
The number of systoles then that must occur in order for the total weight of blood 
to make a complete circuit through the left ventricle will be 608 -f-11 '2 = 54 ; and 
54 systoles at the given pulse-rate will take 27 seconds. 
Vierordt, in his experiments on Dogs, found that the greatest time required for 
a salt injected into the jugular vein to be detected in the blood of the femoral vein was 
21*76 seconds ; his mean result from four experiments was 1 8‘08 seconds. 
The number obtained from our calculation is somewhat higher, as in the nature of 
the case it should be, since Vierordt’s experiments were directed to only one 
of the many paths open to the blood in normal circulation, some of which will require 
MDCCCLXXXIV. U 
