OBSERVATIONS ON THE DIRECT INFLUENCE 
OF VARIATIONS OF ARTERIAL PRESSURE 
UPON THE RATE OF BEAT OF THE MAM- 
MALIAN HEART. By H. NEWELL MARTIN, M. A., 
M. D., D. Sc. With Plate XY. 
The earliest observations on this subject, so far as I know, were 
made by Marey (Recherches sur le pouls an moyen d’un nouvel 
appareil enregistreur. Memoires de la Sociele de Biologic, 1859); 
but as the extrinsic cardiac nerves were not divided in his experi- 
ments, and a rise of blood pressure is now known to stimulate the 
medullary cardio-inhibitory and accelerator nerve centres, the 
results obtained by him give really no information as to the direct 
influence of increased aortic tension upon the rate of the heart’s 
beat. Since then others have experimented, previously dividing 
the extrinsic cardiac nerves, Ludwig and Thiry in 1864 (*Sitzb. d. 
Akad, d. Wissensch. zu Wien) leading the way, but the general result 
is that the matter has been left in a highly unsatisfactory state. 
Some find that variations of arterial pressure have no effect on a 
heart whose venous connections with other parts of the body have 
been severed; others that arterial pressure and pulse rate rise and 
fall together; others that the pulse quickens when arterial tension 
is lowered and vice versa. Finally, Tschirjew {Arch. /. Anal. u. 
Physiologic, Jahrgang 1877, p. 116), the latest writer on the sub- 
ject, finds all of the above effects in different cases; as the result 
of an extensive series of experiments he comes to the conclusion 
that after section of all the extrinsic heart nerve paths, “any con- 
siderable and rapid elevation of blood pressure may directly 
stimulate either the inhibitory apparatus in the heart, or its motor 
ganglia, and the pulse rate accordingly be increased or diminished, 
or in more rare cases remain unaltered.” Such contradictory 
results obtained by a number of competent workers lead naturally 
to the suspicion that some error is involved in the methods of 
experiment employed ; the nature of this error is not, I think, 
far to seek. The methods used to vary arterial pressure have been 
such as cause variations also in several other conditions which 
213 214 
H. NEWELL MARTIN. 
either are known to influence the heart, or may possibly do so; 
nevertheless all these secondary actions have been unheeded: their 
relative prominence in any given experiment has not been noted, 
and any change in the pulse rate has been ascribed solely to the 
changed arterial pressure. Under such circumstances it need 
cause no surprise that very inconsistent results should be obtained. 
The higher aortic pressure is, the more force must be expended 
by the left ventricle in forcing open the semilunar valves; that is 
to say, the higher will be intraventricular systolic pressure. It is 
this influence only of increased aortic pressure which should be 
meant when its direct action upon the cardiac rhythm is spoken 
of; and to get pure results all other consequences of increased 
arterial tension which may influence the heart’s rate of beat must 
be eliminated. This, however, has not been the case in any series 
of experiments with which I am acquainted. 
Arterial pressure has commonly been increased by clamping the 
descending aortic, either in the thorax or abdomen. When this is 
done, however, we alter several other things in addition to arte- 
rial pressure— 
(1.) The amount of blood returned to the right auricle in a 
given time is almost certainly altered, and therefore the rate of 
filling of the heart during diastole. 
(2.) The pressure under which venous blood enters the right 
auricle is probably changed, and therefore intracardiac pressure at 
the end of the diastole. 
(3.) The temperature of the blood returned to the heart by the 
systemic veins and, as a consequence, of the heart itself, is altered. 
The blood returned to the right auricle by the inferior cava is 
known to be warmer than that returned by the superior cava, 
which has not flowed through the hot abdominal organs. When 
the aorta is clamped the heart gets only the cooler superior cava 
blood, as the capillary tracts tributary to the inferior cava are no 
longer supplied with blood. 
(4.) It is known that very slight chemical changes in the blood 
profoundly influence the heart’s beat. To quote.no other instance, 
Gaule has shown that the heart of a frog previously kept in the 
cold and exhibiting deficient functional power, may be restored to 
full vigor by circulating through it the extract of the heart of a 
frog kept previously at a higher temperature. Blood in its flow 
through the abdominal organs experiences important chemical ARTERIAL PRESSURE ON PULSE RATE. 
215 
changes entirely differing from any undergone in other regions of 
body. If, therefore, we circulate blood through head, neck 
and fore limbs only, and return it again and again to the heart 
without exposing it to the action of kidneys, spleen and liver, we 
very soon have a liquid to deal with which is essentially different 
from that which flowed through the heart before the aorta was 
ligated. 
Of course when the arterial pressure is lowered by opening the 
previously clamped aorta all of the above possible disturbing 
actions occur in the opposite direction. 
Another method which has been employed to raise arterial pres- 
sure is to inject blood from another animal into the carotid of the 
animal experimented upon. This also involves several possible 
sources of error. (1) Venous inflow during cardiac diastole is 
almost certainly changed. (2) Venous pressure and, therefore, 
intracardiac diastolic pressure are probably altered. (3) The in- 
jected blood may differ chemically from that already in the vessels, 
and directly act upon the heart. (4) Unless extreme care be 
taken the temperature of the injected blood will be less or greater 
than that of the already circulating blood, and will alter the tem- 
perature and, therefore, the rhythm of the heart. To the above 
objections it may be added that only slight increase of arterial 
pressure can be brought about in this way; as is proved by Worm 
Muller’s experiments. (Arheiten aus d. physiol. Anstalt zu Leip- 
zig, 1873). 
When blood pressure is lowered by bleeding, diastolic inflow 
and pressure are altered, as well as arterial pressure; and also 
probably the chemical metabolisms experienced by the blood in 
its flow through different organs. 
As some one, at least, of the above secondary influences has 
been present in all previous experiments as to the influence of 
variations of arterial pressure upon the pulse rate, it is clear that 
none of these experiments, interesting and important as their 
results are in many cases, are really capable of affording an answer 
to the question in hand, viz: what is the influence, if any, pure 
and simple, of increased aortic pressure {i. e. of increased systolic 
pressure within the left ventricle) on the pulse rate. It is, there- 
fore, not necessary to consider in detail the experiments of pre- 
vious writers. All are vitiated more or less by secondary changes 216 
H. NEWELL MARTIN. 
which have occurred along with the variations of arterial pressure; 
and the number of these possible complications, and their varying 
degree in different experiments, affords a sufficient explanation of 
the contradictory results obtained. 
As regards the frog’s heart, there is more agreement between 
observers, and the experimental conditions have usually been more 
satisfactory. Usually the auricle is supplied steadily with liquid 
of constant composition and at constant pressure from a Marriott’s 
flask; but even here, so far as I know, the arterial cannula has 
always been inserted into the ventricle and, therefore, beyond the 
semilunar valves. As a necessary consequence of this, not only 
systolic ventricular pressure (which normally is the thing changed 
by varied arterial pressure), but also diastolic intraventricular 
pressure has been varied. I accordingly suggested to two of 
my pupils that they should undertake a fresh examination of this 
question by better methods, on the hearts of frogs and chelonia. 
Some results of their work will be found on subsequent pages of 
the present number of this Journal. 
The question involved is clearly one of great importance. In 
almost every experiment relating to cardiac physiology arterial 
pressure is altered: and it is essential to know exactly the direct 
influence of this factor on the heart, before further conclusions can 
be legitimately arrived at. I have, therefore, lately carried out a 
large number of experiments as to the direct influence of variations 
of arterial pressure upon the pulse, making use of the dog’s heart 
completely isolated physiologically from every other organ, but 
the lungs: the method of isolation, which essentially consists in 
closing the whole systemic circulation except that through the 
coronary vessels of the heart itself, was described by me in the 
last number of this Journal (Vol. 11, Xo. 1, p. 119); as the ap- 
paratus has since been modified only in some points of detail, I 
here reproduce, as Plate XV, the figure used in illustrating the 
previous paper, in order to assist in the description of my more 
recent experiments. 
The right and left carotid arteries, o and r, have cannulas placed 
in them, the right subclavian, w, is ligatured, and a cannula is 
put in the left subclavian, m. Then the aorta is ligated imme- 
diately beyond the origin of the left subclavian: the vena cava 
inferior and the azygos vein are tied, and a cannula put in the 
superior cava. Fresh defibrinated strained and warmed blood is ARTERIAL PRESSURE ON PULSE RATE. 
217 
now run in by the superior cava; at the same time the cannula on 
the right carotid is opened, and blood drawn from it until there is 
reason to believe that all the blood originally in the heart and 
lungs of the animal has been washed out; the carotid is then 
again clamped, and the superior cava a few seconds later, when 
the heart and lungs have been tolerably well filled with blood. 
The animal is then transferred to the warm moist chamber, if, 
the cannula of the superior cava is connected with one of the Mar- 
riott’s flasks, 27 or 28, from which a nutrient liquid is sent into 
the heart under a uniform pressure, which in the experiments 
described below was that exerted by a column of blood 10 centi- 
metres in height. The left carotid, o, is connected with the out- 
flow tube, 21, and the cannula in the subclavian with a mercurial 
manometer, 26, the pen of which writes on the paper of a kymo- 
graphion in the usual manner. As soon as one Marriott’s flask is 
empty its connection with the heart is shut otf, and that of the 
other (which has been meanwhile closed) is freed by opening the 
proper one of the clamps, 1 or 2, and closing the other. The 
nutrient liquids employed in the experiments below described were 
(1) fresh defibrinated strained dog’s blood; (2) the same diluted 
with an equal bulk of 0.5 per cent, solution of sodium chloride 
in distilled water. 1 may here state that in other cases I have 
used with success (3) defibrinated dog’s blood with one-third its 
bulk of 0.7 per cent, sodium chloride solution; and (4) defibri- 
nated calf’s blood. 
Under these conditions almost all of the ordinary collateral 
results of increased or lowered arterial pressure can be elimi- 
nated. By closing more or less completely the stop-cock, 22, 
arterial pressure can be raised; by opening the stop-cock wider 
it can be diminished. Meanwhile rate of supply to the right 
auricle, the temperature of the liquid sent into it, and the compo- 
sition of this liquid are unvaried; all these disturbing elements 
are thus got rid of. I have said above that “almost” all secon- 
dary elfects can be eliminated; the almost is due to the varied 
coronary circulation; when aortic pressure is high this must be 
greater than when that pressure is low; so far I see no method of 
eliminating this possible source of error; but in recent years much 
evidence has been accumulated to shew that if the flow of blood 
through an organ is sufficient to nourish it {i. e., does not fall 
below the starvation limit), and is under a lower pressure than 
such as ruptures the vessels or otherwise mechanically impedes 218 
H. NEWELL MAR TIN. 
the action of the organ, there is much reason to believe that varia- 
tions in blood supply have no immediate influence on its functional 
activity. The experiments detailed below give farther support to 
this view: as will be seen, variations of arterial pressure ranging 
between 25 and 150 mm. of mercury have no influence whatever 
upon the heart’s rhythm, although considerably more blood must 
flow through the coronary system under the higher than under the 
lower pressure. 
In the experiments described below the heart was always left in 
the warm chamber at least half an hour before observations were 
made, and longer if the thermometer did not shew that the tem- 
perature was then uniform and had been for some five or ten 
minutes. The animals during the isolation of the heart were 
sometimes placed under the influence of morphia, sometimes of 
curari, and sometimes of chloroform ; these various agents were 
used to eliminate chances of error due the possible toxic action 
of any one of them on a regulatory mechanism in the heart, 
though when fresh unpoisoned defibrinated blood is run for hours 
through the heart after its isolation, there can ’be little doubt 
that any poison absorbed by the organ during the preliminary ob- 
servation is thoroughly washed out. The animals used were small 
dogs, weighing from 6to 7.5 kilos. Uniform artificial respiration 
was kept up by means of a small water engine. 
When temperature had become constant, the connection between 
a full Marriott’s flask (containing about 700 c. c. of liquid) and 
the heart was opened. A minute or two was allowed to elapse, to 
get a steady inflow current; then arterial pressure was raised by 
partially closing the stop-cock, 22, or lowered by opening it wider. 
Tracings were taken for from two to six minutes with arterial pres- 
sures varied in this way; then the observation ceased. Mean- 
while the other Marriott’s flask was filled; and after some minutes 
another observation was made while it was connected with the 
heart; and so on, so often as seemed desirable. In all cases the 
experiment came to an end long before the heart shewed signs of 
abnormal or irregular action ; indeed in most instances it was sub- 
sequently used for preliminary observations on the influence of 
other conditions, as varied venous pressure or varied temperature 
on the pulse rate. 
The results arrived at may be summed up as follows: 
1. When the pressure under which blood of uniform temperature 
and composition is steadily supplied to the right auricle does not ARTERIAL PRESSURE ON PULSE RATE. 
219 
exceed that due to a column of blood ten centimetres in height, no 
variation of arterial pressure which can be brought about by opening or 
closing more or less completely the outflow stop-cock, has any influence 
whatever on the rhythm of a heart isolated from all other organs of 
the body except the lungs, 'provided arterial pressure be not kept at a 
very low level for a considerable time. In other ivords, within very 
wide limits, changes in arterial pressure have no influence whatever 
upon the pulse rate. 
2. If the outflow stop-cock be widely opened and arterial pressure 
lowered to less than twenty millimetres of mercury, this has no direct 
influence on the pulse rate; but it has probably an indirect influence. 
For a minute or more the heart beats recur at the same intervals, but 
after that time, if the low pressure be still maintained, the pulse some- 
times becomes slower, probably from deficient nutrition of the heart 
dependent on insufficient flow through the coronary vessels. 
3. If the pressure at which venous blood enters the right auricle be 
considerable (due to a column of blood forty centimetres in height), 
and if simultaneously the arterial exit be greatly narrowed by closing 
the outflow stop-cock, then arterial pressure at first rises greatly with- 
out any alteration in the pulse rate; but ultimately attains a very 
high level at which the cardiac rhythm becomes extremely irregular. 
Beats occur which somewhat resemble those produced by feeble pneu- 
mogastric stimulation. If the arterial resistance be notv diminished, 
markedly dicrotic beats occur for some twenty or thirty seconds, until 
arterial pressure again falls to a normal level, when the original 
pulse rate is resumed. The conditions when the irregular beats are 
observed are clearly pathological: a filling of the heart under a 
pressure in the venae cavce equal to forty centimetres of blood (twenty- 
nine millimetres of mercury) probably never occurs normally com- 
bined with great arterial resistance. 
In the present article I shall confine myself to what may be 
called normal variations of arterial pressure, that is to say, for 
small dogs, variations between 25 and 160 millimetres of mercury. 
The result under the above heading 2 is undoubtedly abnormal, 
and due to commencing death of the heart; and the results indi- 
cated under number 3 are probably due either to the reception by 
the left ventricle in each diastole of more blood than, under the 
resistance opposed to it, it can pump out in one systole, or to a 
direct stimulation of inhibitory mechanisms in the heart by the 
pathological pressure within the ventricle. This irregular beat 220 
E. NEWELL MARTIN 
with very great arterial resistance has been noted by Haidenhain, 
and I may here state that Knoll’s opinion that it really means 
not a slowed heart beat, but a quick irregular beat which the 
manometer does not properly record, is incorrect; direct observa- 
tion of the exposed heart is conclusive as to the fact that the beats 
are not quick and irregular, but really slow, and frequently dicrotic. 
On the results numbered 2 and 3 above I desire to make further 
observations before publishing detailed conclusions. Hitherto so 
soon as I have observed indications of them I have at once raised 
or lowered arterial pressure so as to prevent death or injury to the 
heart. As regards point 1, the three tables below speak for them- 
selves. They are selected from a dozen experiments which are 
perfectly concordant, and they have been so selected that a dif- 
ferent drug was given to the dog during the preliminary opera- 
tion of isolating the heart in each case. The venous inflow was 
always so proportioned to the resistance to arterial outflow that pres- 
sure in the subclavian during the intervals between any two obser- 
vations was kept at a point from which arterial pressure could be 
considerably raised without the variation passing beyond a physio- 
logical limit; but at the same time, a pressure sufficient to keep 
the heart in a functional condition for a long time. 
Venous pressure in all the experiments recorded below was that 
due to a column of nutrient liquid (defibrinated dog’s blood, or 
the same diluted with an equal volume of sodium chloride solu- 
tion) ten centimetres in height, or very near that; it is not well 
practicable to measure exactly in every experiment the difference in 
level between the cannula in the superior cava and the lower end 
of the tube for the entry of air into the Marriott’s flask; but 
errors of a few millimetres in this regard are of no importance: so 
long as the pressure is constant during an observation a know- 
ledge of its absolute amount within 5 or 6 millimetres of blood 
is of no consequence. 
The tables are constructed as follows: Temperature in the moist 
warm chamber having become constant, the kymographion was 
started and tracings taken for from two to seven minutes. During 
this time the stop-cock, 22, was opened wider, or more closed, or 
opened and then closed, or vice versa, and consequently arterial 
pressure was altered. A number of such observations having 
been made the tables were constructed from the tracings obtained : 
suppose the time to be 2 h., 20r, 10", then arterial pressure is AETERIAL PRESSURE ON PULSE RATE. 
221 
measured at that time and at 2 h., 20', 20". Half the sum of these 
is taken as the mean pressure during the intervening ten seconds. 
The pulse rate is counted for this ten seconds, multiplied by 6, and 
the product given as the rate of heart beat per minute, with the 
mean arterial pressure obtained as above. So far as absolute results 
are concerned, it is seen that the mean arterial pressure arrived 
at in this way is open to some error, and had changes in it been 
accompanied by changes in the pulse rate, more accurate methods 
of arriving at the true mean arterial pressure during each ten 
seconds would have to be employed. But as very great variations 
of mean arterial pressure were used and as the experiments shew 
that none of them, within the limits described above as physio- 
logical, cause any change in the rate of the heart's beat, it is clearly 
unnecessary to resort to planimetry or other troublesome methods 
so as to avoid possible errors of a few millimetres in the measure- 
ments. When gross variations of arterial pressure from 30 to 150 
mm. of mercury cause no change, it is not worth while to spend 
time in endeavoring to exclude possible errors of ten or even 
fifteen millimetres of mercury pressure; and the possible limits 
of error in my measurements never reached the less of those 
quantities. When the lungs are kept well extended and the arti- 
ficial respiration apparatus works with tolerably slow powerful 
blasts, marked respiratory waves are seen on the tracings of arte- 
rial pressure, unless this fall to 50 millimetres of mercury or 
thereabouts, when they disappear. As these rhythmic rises and 
falls of arterial pressure render it more difficult to correctly arrive 
at the mean pressure, I have usually eliminated them by arranging 
my water engine so as to work with rapid short strokes; then res- 
piratory variations of arterial pressure entirely disappear from the 
manometer tracings. 
In the experiments recorded Wow the heart had been physio- 
logically isolated from all other organs but the lungs for some 
considerable time before the recorded observations were made; 
the muscles of the body in general were often already in marked 
rigor before the first observation was made and always long before 
the last. When the words “no record” appear in the details of 
an observation, some one or more of the pens was not writing, so 
that either time, pressure, or pulse rate, could not be determined. 
The temperature given is that of the warm chest in which the 
animal lay. 11. NEWELL MARTIN 
222 
Experiment A. 
October 13, 1881. Small dog, narcotised with morphia during the 
operation of isolating the heart. Nutrient liquid 1,400 cub. cent, of 
defibrinated dog’s blood drawn from two other animals. Arterial pres- 
sure measured in left subclavian. Heart isolated and animal put in 
warm chamber at 4h. 10r, P. M. 
Observation. 
Time. 
Temperature in 
degrees C. 
Arterial Pressure 
in mm. of mercury. 
Pulse Rate 
per minute. 
I. 
o 
o 
31° 
137 
147 
“ 10 
134 
147 
“ 20 
131 
146 
“ 30 
132 
147 
“ 40 
116 
147 
“ 50 
89 
147 
4 h. 45' 00" 
74 
147 
“ 10 
83 
150 
“ 20 
109 
147 
“ 30 
124 
147 
“ 40 
134 
150 
4 h. 46' 00" 
149 
150 
“ 10 
142 
149 
“ 20 
120 
147 
“ 30 
98 
147 
“ 40 
83 
150 
“ 50 
99 
147 
11. 
4 h. 58' 50" 
31° 
133 
147 
4 h. 59' 00" 
134 
149 
“ 10 
139 
147 
“ 20 
143 
150 
“ 30 
144 
150 
“ 40 
142 
149 
“ 50 
138 
149 
5 h. 00' 00" 
136 
148 
“ 10 
129 
150 
“ 20 
104 
150 
“ 30 
82 
150 
“ 40 
87 
150 
“ 50 
117 
151 
5 h. 01' 00" 
123 
148 
“ 10 
129 
151 
“ 20 
133 
150 
“ 30 
130 
150 
“ 40 
110 
150 
“ 50 
90 
151 ARTERIAL PRESSURE ON PULSE RATE. 
223 
Experiment A.—Continued. 
Observation. 
Time. 
Temperature C. 
Arterial Pressure. 
Pulse Rate. 
in. 
5 h. 17' 00" 
31° 
112 
150 
“ 10 
119 
150 
“ 20 
102 
150 
“ 30 
80 
150 
“ 40 
81 
No record. 
“ 50 
100 
150 (?) 
5 h. 18' 00" 
108 
No record. 
“ 10 
114 
150 
“ 20 
119 
150 
“ 30 
125 
No record. 
“ 40 
126 
151 
“ 50 
112 
150 
5 h. 19' 00" 
89 
150 * 
IY. 
5 h. 29' 40" 
31° 
80 
150 
“ 50 
81 
153 
5 h. 30' 00" 
80 
156 
“ 10 
82 
150 
“ 20 
93 
156 
“ 30 
104 
153 
“ 40 
110 
153 
“ 50 
112 
156 
5 h. 31' 00" 
111 
153 
“ 10 
112 
150 
“ 20 
99 
150 
“ 30 
80 
156 
“ 40 
82 
156 
“ 50 
98 
153 
5 h. 32' 00" 
102 
156 
“ 10 
100 
156 
“ 20 
86 
156 
“ 30 
85 
150 
“ 40 
91 
156 
“ 50 
102 
152 
In observation I, arterial pressure varied between 74 and 149 
millimetres of mercury (101 per cent.) and the pulse rate between 
147 and 150 per minute (2 per cent.). In observation 11, arte- 
rial pressure varied between 82 and 144 millimetres of mercury 
(75.6 per cent.) and the pulse rate between 147 and 151 per 
minute (2 per cent.). In observation 111, arterial pressure varied 
between 80 and 126 millimetres of mercury (57.5 per cent.) and 224 
H. NEWELL MARTIN. 
the pulse rate between 150 and 151 per minute (0.66 per cent.). 
In observation IV, arterial pressure varied between 80 and 112 
millimetres of mercury (40 per cent.) and the pulse rate between 
150 and 156 per minute (4 per cent.). 
Experiment B. 
October 15, 1881. Small dog, curarised during the preliminary 
operation. Nutrient liquid 1,350 cub. cent, of defibrinated dog’s 
blood taken from two other animals. Arterial pressure measured in 
left subclavian. Operation completed and animal placed in warm 
chest at 1 h. 50', P. M. 
Observation. 
Time. 
Temperature in 
degrees C. 
Arterial Pressure 
in mm. of mercury. 
Pulse Kate 
per minute. 
I. 
2 h. n/ 
50" 
34.5° 
53.5 
120 
2 h. 18/ 
00" 
78.5 
120 
it 
10 
116.5 
. 120 
ii 
20 
No record. 
No record. 
a 
30 
No record. 
No record. 
ii 
40 
86 
120 
a 
50 
75 
120 
2 h. 19' 
00" 
69 
120 
ii 
10 
66 
120 
a 
20 
80.5 
122 
a 
80 
102.5 
122 
u 
40 
114 
121 
ii 
50 
121 
120 
II. 
2 h. 44/ 
00" 
35° 
53 
117 
U 
10 
57.5 
117 
20 
84 
117 
a 
30 
117 
123 
a 
40 
136 
114 
a 
50 
145 
118.5 
2 h. 45' 
00" 
104 
114 
ii 
10 
67 
118.5 
it 
20 
51 
114 
(I 
30 
49 
117 
ii 
40 
49 
117 
ii 
50 
35 
117 
2 h. 46' 
00" 
27 
114 
ii 
10 
25 
117 
ti 
20 
23 
117 
ii 
30 
22 
114 ARTERIAL PRESSURE ON PULSE RATE 
225 
Experiment B. Observation ll.—Continued. 
Observation. 
Time. 
Temperature C. 
Arterial Pressure. 
Pulse Rate. 
II. 
2 h. 46/ 
407/ 
o 
iO 
CO 
22.5 
114 
U 
50 
22.5 
113 
2 h. 47' 
GO7' 
21 
111 
<( 
10 
20 
111 
(< 
20 
25 
114.5 
a 
30 
45 
110 
III. 
2 h. 54/ 
50" 
35° 
148 
108 
2 h. 55' 
00" 
116 
108 
<( 
10 
18 
112 
It 
20 
56 
108 
it 
30 
43 
109.5 
u 
40 
38 
108 
u 
50 
41 
108 
2 h. 56' 
00" 
51 
108 
Ci 
10 
57 
108 
u 
20 
89 
112 
u 
30 
131 
111 
tt 
40 
143 
110 
IY. 
3 h. 27' 
40" 
35° 
72.5 
99 
<< 
50 
87.5 
102 
3 h. 28' 
00" 
99.5 
100 
(( 
10 
117.5 
99 
<< 
20 
128 
102 
a 
30 
140 
103 
n 
40 
No record. 
No record. 
n 
50 
No record. 
No record. 
3 h. 29' 
00" 
No record. 
No record. 
ft 
10 
91 
102 
a 
20 
73 
102 
u 
30 
59 
102 
u 
40 
43 
102 
u 
50 
44 
102 
Y. 
3 h. 317 
20" 
35° 
63 
98 
U 
30 
81 
102 
u 
40 
98 
98 
it 
50 
110 
99 
3 h. 33' 
00" 
119 
100 
<< 
10 
No record. 
No record. 
<< 
20 
No record. 
No record. 
n 
30 
No record. 
No record. 
it 
40 
No record. 
No record. 226 
H. NEWELL MARTIN. 
Experiment B. Observation Y.—Continued, 
Observation 
Time. 
Temperature C. 
Arterial Pressure. 
Pulse Kate. 
Y. 
3 h. 32' 
50" 
35° 
127 
101 
3 h. 33' 
00" 
106 
102 
(( 
10 
70 
102 
ll 
20 
54 
101 
ll 
30 
47 
99 
ll 
40 
55 
100.5 
ll 
50 
72 
103 
3 h. 34/ 
00" 
89 
102 
ll 
10 
104.5 
102 
n 
20 
112.5 
101.5 
n 
30 
122 
103 
u 
40 
130 
102 
n 
50 
131 
103 
3 h. 35' 
00" 
111 
104 
ll 
10 
80 
102 
U 
20 
65 
100 
il 
30 
40 
102 
ll 
40 
51 
102 
ll 
50 
56 
102 
YI. 
3 h. 40' 
55" 
35° 
50.5 
102 
3 h. 41/ 
05" 
58.5 
101 
it 
15 
64 
102 
ll 
25 
64 
102 
il 
35 
66 
102 
ll 
45 
80 
102 
ll 
55 
100 
102 
3 h. 42' 
05" 
114 
102 
It 
15 
101 
102 
ll 
25 
71 
3 02 
U 
35 
61 
102 
ii 
45 
75.5 
103 
ll 
65 
98.5 
102 
3 h. 43/ 
05" 
112 
104 
il 
15 
102 
103 
ll 
25 
74 
102 
ll 
35 
56 
101 
ll 
45 
45 
100 
U 
55 
33 
102 
3 h. 44' 
05" 
25 
102 
ll 
15 
23 
102 
ll 
25 
22 
104 
ll 
35 
18.5 
102 
ll 
45 
17.5 
103 ARTERIAL PRESSURE ON PULSE RATE. 
227 
In observation I of the above experiment arterial pressure 
varied between 53.5 and 116.5 millimetres of mercury (117 per 
cent.) and the pulse between 120 and 122 per minute (1.6 
per cent.). In observation 11, arterial pressure varies between 
20 and 145 millimetres of mercury (625 per cent.) and the pulse 
rate between 110 and 118.5 per minute (nearly 8 per cent.); 
this it will be seen on closer examination is one of the cases 
above referred to, which lead to the suspicion that a continued 
arterial pressure (as measured in the subclavian) of less than 
30 millimetres of mercury is insufficient to nourish ,the heart 
and leads to a slowing of its beat. Arterial pressure was kept 
below this limit for nearly one and a half minutes, and the pulse 
rate fell from 117 to 110. In observation 111, arterial pressure 
varies between 38 and 148 millimetres of mercury (290 per cent.) 
and the pulse rate between 108 and 112 per minute (3.6 per 
cent.). In observation IV, arterial pressure varies between 43 
and 140 millimetres of mercury (225.5 per cent.) and the pulse 
rate between 99 and 103 per minute (4 per cent.). In observation 
V, arterial pressure varies between 40 and 111 millimetres of 
mercury (177.5 per cent.) and the pulse rate between 100 and 
104 per minute (4 per cent.). In observation VI, arterial pres- 
sure varies between 17.5 and 114 millimetres of mercury (551.5 
per cent.) and the pulse rate per minute between 100 and 104 
(4 per cent.). 
Experiment C. 
October 26, 1881. Small dog, anaesthetised by chloroform during 
the operation of isolating the heart. Nutrient liquid 800 c. c. of de- 
fibrinated dog’s blood mixed with 800 c. c. of 0.5 per cent, solution of 
pure sodium chloride in distilled water. Heart isolated and animal 
placed in warm chest at 12 h. 50', P. M. When the series of obser- 
vations detailed below was concluded the heart was still in good con- 
dition and was used for two hours for other experiments. 
Observation. 
Time. 
Temperature in 
degrees C. 
Arterial Pressure 
in mm. of mercury. 
Pulse Eate 
per minute. 
I. 
1 h. 23' 
10" 
3t° 
29 
102 
it 
20 
30 
103 
it 
30 
30 
102 
u 
40 
30 
102 228 
II NEWELL MARTIN. 
Experiment C. Observation I.— Continued. 
Observation. 
Time, 
Temperature C. 
Arterial Pressure. 
Pulse Rate. 
I. 
1 h. 23' 
50" 
37° 
33 
103 
1 h. 24/ 
00" 
40 
102 
It 
10 
46 
103 
20 
51 
102 
ll 
30 
59 
102 
n 
40 
63 
103 
u 
50 
56 
101 
1 h. 25' 
00" 
46 
102 
u 
10 
40 
102 
u 
20 
35 
103.5 
u 
30 
42 
102 
u 
40 
58 
103 
it 
50 
70 
102 
1 h. 26/ 
00" 
79 
105 
ll 
10 
80 
104.5 
u 
20 
No record. 
No record. 
ll 
30 
40 
105 
u 
40 
36 
105 
50 
26 
105 
II. 
1 h. 33' 
20" 
37° 
40 
100 
u 
30 
42 
101 
ll 
40 
43 
102 
n 
50 
44 
102 
1 h. 34/ 
00" 
37 
102 
il 
10 
30 
102 
ll 
20 
25 
102 
ll 
30 
25 
101 
ll 
40 
28 
101 
ll 
50 
29 
101 
1 h. 35' 
00" 
28 
102 
ll 
10 
27 
102 
ll 
20 
29 
101 
ll 
30 
39 
100.5 
It 
40 
62 
102 
ll 
50 
63 
102 
1 h. 36' 
00" 
72 
102 
ll 
10 
56 
102 
ll 
20 
32 
102 
ll 
30 
29 
101.75 
ll 
40 
41 
101 
ll 
50 
58 
102 
1 h. 37' 
00" 
68 
102 
ll 
10 
78 
103 
ll 
20 
87 
103 ARTERIAL PRESSURE ON PULSE RATE. 
229 
Experiment C. Observation ll.—Continued. 
Observation. 
Time. 
Temperature C. 
Arterial Pressure. 
Pulse Kate. 
II. 
1 h. 3V 30" 
31° 
93 
105 
“ 40 
98 
102 
“ 50 
101 
102 
1 h. 38' 00" 
103 
102 
“ 10 
88 
102 
“ 20 
53 
102 
“ 30 
29 
102 
“ 40 
25 
101 
“ 50 
25 
100.5 
1 h. 39' 00" 
24 
100.5 
“ 10 
24 
102 
“ 20 
26 
102 
“ 30 
27 
102 
“ 40 
26 
100.5 
“ 50 
28 
100.5 
III. 
1 h. 57' 30" 
37° 
28 
96 
“ 40 
38 
94 
“ 50 
'# 
24.5 
97 
1 h. 58' 00" 
29.5 
95 
“ 10 
33 
96 
“ 20 
25 
96 
“ 30 
14.5 
99 
“ 40 
12 
95 
“ 50 
14.5 
96 
1 h. 59' 00" 
20 
96 
“ 10 
24.5 
96 
“ 20 
29 
96 
“ 30 
34 
98 
“ 40 
37.5 
99 
“ 50 
30 
96 
1Y. 
2 h. 02' 10" 
37° 
51 
100 
“ 20 
64 
100.5 
“ 30 
64 
100.5 
“ 40 
76 
102 
“ 50 
87 
102 
2 h. 03' 00" 
94 
102 
“ 10 
89 
103 
“ 20 
56 
105 
“ 30 
30 
102 
“ 40 
• 
37 
102 
“ 50 
54 
105 
2 h. 04' 00" 
70 
108 
“ 10 
81 
104 230 
H. NEWELL MARTIN 
Observation. 
Time. 
Temperature C. 
Arterial Pressure, 
Pulse Bate. 
IY. 
2 h. 04' 
20" 
37° 
89 
104 
tt 
30 
95 
106 
il 
40 
99 
105 
a 
50 
106 
105 
2 h. 05' 
00" 
81 
105 
<( 
10 
39 
105 
il 
20 
21 
105 
a 
30 
24 
104 
it 
40 
35 
105 \ 
tt 
50 
50 
108 
2 h. 06' 
00" 
64 
105 
it 
10 
77 
108 
<< 
20 
88 
109 
<< 
30 
81 
110 
tt 
40 
48 
108 
il 
50 
23 
108 
2 h. 07' 
00" 
27 
108 
a 
10 
42 
107 
it 
20 
59 
109 
tt 
30 
73 
110 
it 
40 
83 
111 
a 
50 
77 
109 
2 h. 08' 
00" 
No record. 
No record. 
it 
10 
19 
109 
it 
20 
18 
109 
il 
30 
19 
109 
Y. 
2 h. 17' 
20" 
37° 
25 
105 
tt 
30 
26 
108 
it 
40 
29 
105 
50 
33 
105 
2 h. 18' 
00" 
40 
106 
it 
10 
49 
106 
It 
20 
53 
106 
ft 
30 
57 
106.5 
it 
40 
63 
106.5 
tt 
50 
68 
106.5 
2 h. 19' 
00" 
71 
106.5 
tt 
10 
72 
106 
It 
20 
73 
106.5 
il 
30 
76 
108 
(I 
40 
77 
106 
It 
50 
78 
107 
2 h. 20' 
00" 
77 
105 
ft 
10 
53 
105 
Experiment C. Observation IY.—Continued. ARTERIAL PRESSURE ON PULSE RATE. 
231 
Experiment C. Observation Y.— Continued. 
Observation. 
Time. 
Temperature C. 
Arterial Pressure. 
Pulse Eate. 
Y. 
2 h. 20' 20" 
37° 
29 
105 
“ 30 
23 
105 
“ 40 
22 
105 
“ 50 
24 
105 
2 h. 21/ 00" 
30 
105 
“ 10 
39 
105 
“ 20 
45 
106.5 
“ 30 
53 
105 
“ 40 
61 
106.5 
“ 50 
66 
106.5 
2 h. 22' 00" 
71 
106.5 
“ 10 
No record. 
No record. 
“ 20 
No record. 
No record. 
“ 30 
76 
106.5 
“ 40 
69 
106.5 
“ 50 
46 
106.5 
2 h. 23' 00" 
26 
106.5 
“ 10 
22 
106.5 
“ 20 
21 
106.5 
“ 30 
20 
106.5 
In observation I of the above experiment, arterial pressure 
varied between 26 and 80 millimetres of mercury (207 per cent.) 
and the pulse between 101 and 105 per minute (4 per cent.). In 
observation II arterial pressure varied between 24 and 103 milli- 
metres of mercury (329 per cent.) and the pulse rate between 100 
and 105 per minute (5 per cent.). In observation 111, arterial 
pressure varied from 12 to 38 millimetres of mercury (216.5 per 
cent.) and. the pulse rate from 94 to 99 per minute (5 per cent.). 
In observation IV, arterial pressure varied between 18 and 106 
millimetres of mercury (863 per cent.) and the pulse rate between 
100 and 111 per minute (11 per cent.). In observation V, arterial 
pressure varied between 20 and 78 millimetres of mercury (290 
percent.) and the pulse rate between 105 and 108 per minute (less 
than 3 per cent.). 
A critical examination of the preceding tables will, I think, 
shew conclusively that variations in arterial pressure within the 
limits indicated in them have no influence on the pulse rate of the 232 
H. NEWELL MARTIN. 
isolated dog’s heart. In the great majority of cases the variations 
in the pulse rate fall clearly within the limits of error of the 
experiment (2-3 per cent.), while arterial pressure is greatly varied. 
Eliminating the obviously exceptional observations 11, Expt. B, 
and IV, Expt. C, the average variation of arterial pressure in an 
observation was 204 per cent., and the average variation in the 
pulse rate 3.3 per cent. 
That the possible sources of error will readily account for the 
pulse changes in most cases is clear when it is remembered 
(1) that a mistake of one-sixth of a beat in counting out the pulse 
in any period of ten seconds appears in the tables as an error of 
one beat per minute; (2) that the temperature of the air pumped 
through the lungs and influencing the temperature of the blood 
■was often unavoidably altered during the course of an observation 
as the doors of my present experiment room, which unfortunately 
is somewhat of a thoroughfare, were opened by passers-by from 
time to time. The latter influence is of great importance, as 
experiments which I hope shortly to publish, have proved that 
the dog’s heart is, so far as its rhythm is concerned, extremely 
sensitive to slight variations in temperature. 
* Whatever the cause of the slight pulse-rate changes observed 
may be, it is at least clear that they are not dependent on varied 
aortic pressure, for there is no possible relationship, direct or 
inverse, to be detected between the two, when the whole series of 
observations is examined. In most cases great variations of arte- 
rial pressure are seen to occur without any change in the pulse 
rate, and then, a little later in the same observation perhaps, the 
pulse alters two or three beats a minute without any considerable 
simultaneous change in arterial pressure. 
If the relationship between pulse rate and arterial pressure were 
invariable, even 3.3 per cent, of variation in the pulse per minute 
might clearly be significant: but as there is no such constant rela- 
tionship, and the known sources of error fully account for such 
pulse-rate variations as were observed, they obviously mean nothing 
in this connection: and we may safely conclude that within the 
limits of aortic pressure indicated by pressures varying between 85 
and IJ/J millimetres of mercury in the subclavian, no change of 
pressure has any direct action upon the rate of beat of the isolated 
heart of the dog. ARTERIAL PRESSURE ON PULSE RATE. 
233 
Before concluding it is my duty and pleasure to acknowledge 
the willing and skilful assistance in the execution of ray experi- 
ments rendered to me by Mr. H. H. Donaldson and Mr. Mactier 
Warfield, who not only undertook the tedious task of getting 
ready the apparatus for each experiment, but gave me most im- 
portant help in carrying it through. STUDIES FROM BIOL, LAB, 
YOL, 11, - PLATE XV.