156 
MESSRS. W. H. HOWELL AND E. DONALDSON 
June 2, 1882.—Weight of Dog, 6085 grms. 
Observations. 
Venous pres 
aur 
Centims. of 
blood. 
;ure in right 
icle. 
Millims. of 
mercury 
Pressure in left auricle in 
millims. of mercury. 
1 
10 = 
= 7-8 
Mean. 
8 
Max. 
2 
20 = 
= 15-6 
10 
3 
30 = 
= 23-3 
12 
4 
40 = 
= 311 
13-5 
15'5 
5 
50 = 
= 38-9 
15 
19 
6 
60 = 
= 467 
16 
20 
7 
50 = 
= 38-9 
15 
20 
8 
40 = 
= 3L1 
14 
18 
9 
30 = 
= 23-3 
13 
16 
10 
20 = 
= 15-6 
10 
12-5 
11 
10 = 
= 7-8 
8 
10 
It is seen that the mean intra-auricular pressure of the left heart at the highest 
venous pressure used was only 16 millims. of mercury, which, as we have before said, 
is probably inside the limits which auricular pressure may reach during life, that is, 
if the left auricle is exposed to as great a pressure as the right, and there is no 
reason for supposing that it is not. We did not think it necessary to apply the 
corrections to the tables given of the effect of venous pressure upon the work done 
by the left ventricle, since except for the purpose of constructing a curve of work 
the absolute value of the work done by the contracting ventricle is of no especial 
importance. 
IV. 
Influence of rate of beat on the work done by the heart. 
In endeavouring to arrive at a conclusion as to the average quantity of blood 
thrown out from the ventricle of Man’s heart at each systole upon the basis of the 
results obtained from the Dog, we were led, as has been said, to consider the 
influence of pulse-rate upon this quantity. 
Looking over the literature of the subject as far as it has been accessible to us, 
we find that no definite knowledge has been gained upon this point. Volkmann, 
in discussing the effect of changes of pulse-rate upon the mean velocity, says that 
he can make no definite statement of the relations between the two. By bleeding 
his animals he got a diminished velocity together with an increased pulse-rate, but 
it is evident that from such a method of operating no causal relation can be assumed 
to exist between these two factors. 
By cutting the vagi and thus producing a much more rapid pulse, he found that in some 
