144 
MESSRS. W. H. HOWELL AND F. DONALDSON 
Observations on the preceding table. —In experiment 1, April 4th, it is probable that 
the limit was not quite reached, as will he seen by referring to the complete record of 
that experiment (see Section III.) ; the apparatus at that time being arranged so 
that 36’8 centims. was the highest venous pressure that could he obtained. 
In experiment 4, April 18th, the limit was practically reached at a venous pressure 
of 60 centims. The right auricle then received all the blood the heart could pump out. 
In experiment 7, May 30th, we are not positive that the limit was completely 
reached, no higher venous pressure than that recorded was tried, on account of the 
object for which the experiment was performed (see Section IV.). This experiment 
was introduced into this table, since it had been found in the other experiments 
that the maximum outflow from the aorta was obtained at or below a venous 
pressure of 60 centims. Since the Dog in this case was somewhat larger than those 
usually experimented upon, it is possible that a larger outflow might have been 
obtained at a higher venous pressure. 
The ratio of the weight of blood thrown out at each systole to the weight of 
the animal is given in the following table. The specific gravity of the defibrinated 
Calf’s blood is taken as 1050 ; an accurate determination in one case gave 1047. 
April 4. 5*79 X 1*05= 6-08 -=-5891 = ‘00103 
„ 13. 8-67X 1-05= 9 "10 4- 8125 = "00112 
„ 18. 8-25 x 1-05= 8-66-^-7725=-001 12 
May 2. 10‘97xl'05 = ll-52^8610='00134 
„ 9. 5-94x 1-05= 6-24-t- 5645 =-00111 
„ 30. 9-31 X 1-05= 9’78-i- 9555 =‘00102 
The agreement amongst the results is as close as could be expected, when we 
remember the number of disturbing conditions which may come into play. 
One of the most important causes of variation, the value of which we did not fully 
recognise until our experiments had nearly drawn to a close, is to be found in the 
pulse-rate ; this, as will be shown in Section IV., exercises a marked influence on the 
amount of blood thrown out at each systole. 
Omitting the experiments of April 4th and May 30th, since in both cases the 
maximum was not quite reached, we find that the mean ratio of the maximum weight 
of blood thrown out from the left ventricle at a single systole to the whole body weight 
is ‘00117 or -g-g-g, for a mean pulse-rate of 180 per minute. 
Since the slowing influence of the vagi is removed from a heart isolated in this 
way, the pulse-rate of course is greater than in the normal Dog. 
The average pulse-rate in a living Dog may be taken as about 120 per minute. We 
have as yet only one experiment, that of May 30th (see Section IV.), to show what 
the maximum outflow at each systole is when the heart is beating at this rate. 
According to that experiment the ratio of the maximum weight of blood forced out 
