148 
MESSRS. W. H. HOWELL AND F. DONALDSON 
pressure at the height at which the maximum outflow from the left ventricle was 
obtained, since in this case we believe that the left ventricle works under conditions 
most closely resembling those to which it is subject during life ; but owing to the 
rapidity with which our flasks were emptied at these high pressures, and other 
mechanical difficulties, this was not attempted. 
The heart was allowed to work for a short time, from one to two minutes, at each 
given arterial pressure before an observation was made. 
We give below two examples of the results obtained; several other experiments 
were made, but the two given were those in which the heart and lungs were in the 
best condition, and the pulse-rate remained very nearly constant. 
The work done in gramme-meters at each systole of the left ventricle at various 
arterial pressures is given in the last column, and was calculated by multiplying 
the amount of blood thrown out at each systole into the height to which it was 
r raised, making of course the necessary corrections for the specific gravity of the 
H S AH S 
blood used. The formula which we employed is W=A.s.jqqq • 100 O ’ * n W ^' LC ^ ^ 
represents the work done, A the quantity in cubic centimetres thrown out from the 
ventricle at each systole, H the arterial pressure in millimetres of mercury, S the 
specific gravity of mercury, and s the specific gravity of the blood. 
The arterial pressure was measured in the carotid, and is no doubt a little less than 
that at the root of the aorta. 
In both the experiments given the observations upon arterial pressure were made 
after a series of observations at different venous pressures had been taken, the results 
of which are given in detail in Section III. under the same dates. 
Table showing the effect of variations of arterial pressure on the work done by 
the heart. 
April 13, 1882.—Weight of Dog, 8125 grms. Weight of heart, 92 grins. 
Observations. 
Time, f.m. 
Temp. C. 
in superior 
cava. 
Beats in 
30 seconds. 
Arterial 
pressure in 
carotid. 
Millims. of 
mercury. 
Venous 
pressure in 
superior cava. 
Oentims. of 
blood. 
Outflow in 
30 seconds. 
Cub. centims. 
Outflow in 
1 beat. 
Cub. centims. 
Work done 
at each 
systole of 
the left 
ventricle 
in gramme- 
metres. 
h. 
m. 
1 
2 
14 
3575 
83-5 
112 
20 
375 
4-49 
6-78 
2 
2 
16 
35-25 
78-5 
88 
20 
360 
4-58 
5 "45 
3 
2 
19 
36 + 
80 
62 
20 
379 
4'74 
3-97 
4 
2 
21 
36 + 
81-5 
92 
20 
367 
4-50 
5"59 
5 
2 
24 
36 + 
82 
120 
20 
367 
4-48 
7-25 
6 
2 
26 
36-5 
82 
142 
20 
355 
433 
8-30 
7 
_• 
2 
28 
36-5 
82 
108 
20 
357 
4-35 
6 - 34 
