NOTE ON THE PHYSIOLOGY OF THE CARDIAC 
NERVES OF THE CALF 
v BY 
REID HUNT and D. W. HARRINGTON 
(From the Physiological Laboratory of Columbia University at the 
College of Physicians and Surgeons, New York) 
F ROM 
THE JOURNAL OF EXPERIMENTAL MEDICINE 
Vol. II, No. 6, 1897 BOTE OB THE PHYSIOLOGY OF THE CAEDIAC BEEVES 
OF THE CALF. 
By REID HUNT and D. W. HARRINGTON. 
(From the Physiological Laboratory of Columbia University at the College of 
Physicians and Surgeons, New Yoik.) 
We were able to experiment upon but one calf, and had we any 
expectation of continuing this investigation in the near future we 
should not publish the results of this experiment at present. Our 
results, however, seem to us so satisfactory and conclusive that we 
feel justified in describing them. The heart of the calf is so large 
and the rate of beat so slow that every change can be followed by 
the eye with great ease, and the effects of stimulating various nerves 
can be determined more satisfactorily in some respects than when 
recording apparatus is applied to the smaller and more rapid hearts 
of the animals ordinarily used in the laboratory. 
The calf upon which we experimented had been used by Or. Curtis 
in a lecture demonstration and had been under the influence of ether 
for some time, but the heart was beating vigorously, and the blood 
pressure, which was recorded by the mercury manometer in the usual 
manner, was moderately high (100 mm. of mercury). 
Stimulation of the vagus.—Stimulation of the peripheral end of 
the vagus with currents of moderate intensity caused slowing of both 
auricle and ventricle. In a number of cases, however, the ventricle 
was slowed very decidedly, while the rate of the auricle was but 
slightly affected. This result agrees with that described by Franck* 
for the dog, but differs from the results obtained by most experiment- 
ers for this animal. McWilliam, f Bayliss and Starling,:}: and Boy 
and Adami,§ for example, speak of the auricles in the dog as being 
* Franck, Archives de Physiologie, 5. s., ii (1890), 403. 
f McWilliam, Journal of Physiology, ix (1888), 345. 
t Bayliss and Starling, ib. xiii (1892), 407. 
§ Roy and Adami, Phil. Trans., clxxxiii (B), (1892), 199. 724 
Physiology of the Cardiac Nerves of the Calf 
more easily slowed by stimulation of the vagus than are the ven- 
tricles. In none of the several stimulations of the vagus in the calf 
did we observe a slowing of the auricles without a slowing of the 
ventricles also. 
It is interesting to note that sometimes there was an after-effect of 
the stimulation of the vagus in which the effect upon the ventricle 
was more marked than that upon the auricles. Thus in one case, after 
a long-continued stimulation of the vagus, during which auricles and 
ventricles were both slowed but continued to beat together, the ven- 
tricles did not return to their normal rate, while the auricles did 
return, and it was observed that the ventricles were following at 
times every auricular beat, and at other times only every second beat. 
While this slow rate of the ventricles continued, the accelerators were 
stimulated and the ventricles began at once to follow all the auricular 
beats. The rate of the auricles, however, was but slightly increased. 
After the cessation of the stimulation of the accelerators the slow 
irregular beat of the ventricles returned. 
Apparently these results and similar ones obtained in the experi- 
ments upon the opossum can be explained satisfactorily by supposing 
the conductivity of the muscle fibres connecting the auricle and ven- 
tricle to have been altered by the stimulation of the nerves.* After 
the prolonged stimulation of the vagus, the conductivity of these 
muscle fibres seemed to be depressed for some time; stimulation of 
the accelerators apparently caused a temporary increase of their irri- 
tability, and as a consequence the ventricle followed every auricular 
beat. So, also, the decreased conductivity of these fibres resulting 
from the action of the vagus may explain why stimulation of these 
nerves at times caused a slowing of the ventricles while the auricles 
were not much affected. Possibly this factor—the changes in the 
conductivity of the muscle fibres between the auricles and ventricles— 
has not received sufficient attention from some of the physiologists 
who have discussed the relative effects of the stimulation of the vagus 
and accelerator nerves upon the different parts of the heart. 
* Cf. Gaskell, Journal of Physiology, iv (1883), 100; McWilliam, op. cit. 367; 
Bayliss and Starling, op. cit. 412. Reid Hunt and D. W. Harrington 
725 
Stimulation of the peripheral end of the vagus with a very weak 
current caused in one or two cases a slight acceleration of the heart, 
as is often observed in the dog. 
Accelerator nerves.—"VVe stimulated two nerves passing from the 
spinal nerves to the stellate ganglion—the ramus communicans from 
the second spinal nerve and a nerve accompanying the vertebral 
artery (the “ nervus vertebralis ”). Stimulation of both of these 
nerves caused acceleration of the heart; the results differed, however, 
in a very interesting manner according as one or the other nerve was 
stimulated. The immediate effect of stimulating the vertebral nerve 
was to cause an acceleration of the auricles, but a slowing of the ven- 
tricles due to failure of the latter to follow all of the beats of the 
former. Frequently, if the stimulation was continued for some time, 
the ventricles began to follow all the auricular beats. We have in 
this case an illustration of how stimulation of the accelerator nerves 
can cause an actual slowing of the ventricles—a possibility recently 
pointed out by Engelmann.* This primary slowing was always 
obtained whatever the strength of the stimulus used; the acceleration 
of the auricles and the slowing of the ventricles was most' marked, 
however, with strong stimuli. 
Stimulation (x-s) of the vertebral nerve ; the secondary coil was 12 cm. from 
the primary. In the early part of the stimulation the ventricles failed to 
follow all the auricular beats, and the result was a slight slowing of the 
pulse; later there was an acceleration, the ventricles now beating at the same 
rate as the auricles. Time in intervals of 10 seconds. Curve to be read from 
left to right. 
During the stimulation, the result of which is shown in the accom- 
panying figure, the secondary coil of the induction apparatus was 12 
cm. from the primary coil; the rate of the auricles and ventricles 
* Eng-elmann, Pfiiiger’s Archiv, lxv (1896), 161. 726 
Physiology of the Cardiac Nerves of the Calf 
before stimulation was 20 beats in 10 seconds. In tlie first 10 seconds 
during stimulation the auricle gave 24 beats, the ventricle but 19, as 
it failed to follow all the auricular beats; in the second period of 10 
seconds both auricle and ventricle gave 26 beats and the latter fol- 
lowed the former throughout. In a second stimulation the stimulus 
was stronger, the coil being at 10 cm., before stimulation the auricle 
and ventricle were beating at the rate of 19-J in 10 seconds; during 
stimulation the auricles beat at the rate of 26 in 10 seconds, while 
the ventricles, following only every second auricular beat, had a rate 
of 13 in 10 seconds. Later the rate of the ventricle became more 
rapid, following all the auricular beats. 
The effect upon the heart of stimulating the 2nd ramus com- 
municans differed from the above in that both auricle and ventricle 
were uniformly accelerated. The following figures give the result of 
stimulating the 2nd ramus communicans with the coil at 10 cm. (the 
same strength of current as was used in the second of the above stimu- 
lations of the vertebral). The rate of both auricle and ventricle be- 
fore stimulation was 20 in 10 seconds; during the first 10 seconds the 
rate increased to 234, during the second 10 seconds it was 28, during 
the third, 28-J, and during the first 10 seconds after stimulation it 
was 294. Throughout the stimulation each auricular beat was fol- 
lowed by a ventricular beat, and this occurred also when stimuli of 
various intensities were used. 
The above facts show that in this individual at least the accelerator 
fibres passing through the vertebral nerve were different from those 
in the 2nd ramus communicans; stimulation of each nerve caused 
acceleration of the auricle, but the fibres of the 2nd ramus com- 
municans evidently had more effect upon the ventricle than did those 
of the vertebral. This difference may be explained by supposing 
that the ramus communicans contained more fibres passing to the 
ventricle than did the vertebral nerve, or, and this is perhaps more 
probable, by supposing that it contained more fibres, stimulation of 
which caused the conductivity of the muscle fibres connecting the 
auricles and ventricles to be increased. In any case, it is certain that 
the accelerator fibres in the two nerves differed in either their ana- Reid Hunt and D. W. Harrington 
727 
tomical or physiological relations to the heart. Bayliss and Starling* 
observed a similar separation of the functions of the accelerator fibres 
in the dog and ascribed the result to the earlier fatigue of one set of 
fibres; the element of fatigue can probably be excluded from our 
experiment upon the calf, for both nerves had received the same 
treatment. 
We also tried the effect of stimulating the inhibitory and accele- 
rator nerves simultaneously. The peripheral end of one vagus was 
stimulated with an induced current produced by the slow interrup- 
tion of the primary current with the “ Schlagwahler ”; both auricles 
and ventricles were slowed. While the stimulation of the vagus was 
continued the accelerators were stimulated; the rate of both auricles 
and ventricles was accelerated. 
Thus the antagonism of the inhibitory and accelerator nerves, 
already found to hold in the case of the ventricles of other animals, is 
found to occur in the calf also, and holds for the auricles as well as 
for the ventricles.f 
* Bayliss and Starling, op. cit. p. 416. 
f Since the completion of my paper upon the relation of the inhibitory to 
the accelerator nerves of the heart (Journal of Experimental Medicine, ii 
(1897), 151), I have repeatedly observed directly the effect upon the auricle 
and ventricle of the simultaneous stimulation of these nerves in the dog. 
With the strength of current which I used, a ventricular always followed 
an auricular beat, and in all cases the effect upon the rate of the auricle as 
well as upon that, of the ventricle, was approximately the algebraic sum of 
the effects produced by stimulating the nerves separately. An “ indepen- 
dent ventricular rhythm ” which might complicate the results was never 
caused by the stimulation of the vagus in my experiments.-—R. H.