applied to this nerve within the cranium, that
the pupil became dilated, remaining so for a
considerable time after stimulus had been
withdrawn, and then again slowly contracting.
The effects thus produced upon the iris are,
according to him, analogous to those pro-
duced upon the heart by application of the
galvanic stimulus to the pneumogastric. More-
over, the nerves which are sent to the heart
of the frog do not present the arrangement
which Weber has described. No other fila-
ments than those which pass from the vagus
are distributed to the heart of this animal, at
least no others have been demonstrated. The
vagus nerve becomes united with the sympa-
thetic in the ganglion, which is situated about
one line from the root of the pneumogastric ;
and from this ganglion, which contains fibres of
the vagus and sympathetic, springs, amongst
other branches, a slender filament which is
destined for the heart. This runs down-
wards on the inner aspect of the lungs, and
passes along the veins to the auricles and
ventricle, the former receiving the greater
number of the nerve fibres. The branch in
* Wagner's Handworterbuch, band iii. p. 415.
SYMPATHETIC NERVE.
461
question contains fibres derived both from
the sympathetic and also from the pneumo-
gastric. Again, such a restraining power must
hold an opposite relation to the moving power
in the normal condition ; the moving power
would therefore express itself only in part,
according as the other is in a latent state or
in a state of activity, and consequently sec-
tion of the vagus nerve ought, did it exert
the restraining power in question, to be fol-
lowed by an acceleration in the movements
of the organ, which is not the case. Budge,
therefore, seems to regard the fibres which
are sent to the heart in the frog by the pneu-
mogastric, as possessed of motor and sensory
properties.
Schift* also found that when the heart's
action has been made to cease by application
of the wires to the groove between the au-
ricles and ventricles, this effect cannot be
counteracted by applying them to the bulbus
arteriosus. The phenomenon of the cessa-
tion of the heart's action, produced by the
application of the galvanic stimulus to the
pneumogastric, he explains by supposing
that its fibres are in a state of activity
during the systole of the corresponding
part of the heart, but quickly become ex-
hausted, thus allowing the diastole to take
place: thereafter, their activity being again
renewed, a second systole results. When
therefore, strong galvanic stimuli are applied
to the nerve the state of exhaustion continues
longer and in the same proportion the dia-
stole, or cessation of the heart's action, is also
longer.
In accordance with the above views, Valen-
tin * in like manner holds that the sympa-
thetic has no influence over the movements
of the heart in the frog, neither giving rise to
acceleration nor stoppage of its action.
In regard to the connection between the
central masses of the nervous system and the
action of the heart, it is evident, from what
has been above stated in regard to the effects
which are produced by the application of the
galvanic stimulus to the pneumogastric nerve,
that a certain influence must be exercised by
these. By Willis f, and others, it was held
that the movements of the heart, as well as
of the other inorganic muscles, depend upon
the cerebellum. "This they believed from the
circumstance that the nerves which preside
over the involuntary actions were supposed
to take their origin from this part of the ner-
vous system, and also from observing that
wounds upon the back part of the head proved
speedilv fatal. HallerJ, again, endeavoured
to show that the action of the heart is en-
tirely independent of nervous influence, and is
due merely to the inherent irritability of the
muscular fibres. From the circumstance that
sudden destruction of the spinal cord im-
mediately produces an interruption of the
heart's action, Legallois concluded that its
* Loc. cit. p. 694.
f Cerebr. Anatomia Xervorumque Descript. et
Usus, p. 195.
J Dissertat. sur 1'Irritabilite, t. i. p. 72.
movements are not due to inherent irritability,
as Haller maintained, but depend upon the
spinal cord. The cessation produced in the
way just stated, although indicating that an
influence may be exercised through the cen-
tral nervous masses upon the movements of
the heart, by no means implies the conclusion
which was drawn from it by Legallois, in-
asmuch as the heart may sometimes in such
cases again begin to pulsate. That the heart
may be influenced in its action through the
medium of the central masses of the nervous
system is also shown by the effects which are
produced by the application of the galvanic
stimulus to these parts. Thus, in the frog,
as shown by the experiments of Weber*,
Budge-j-, Valentin , and others, it may be
made to cease pulsating by applying the wires
of the magneto-electric rotation apparatus to
either side of the medulla oblongata. Unless
there has been much loss of blood in exposing
the parts the heart becomes dark-red, and is
very much distended; where the large blood-
vessels have been previously cut the heart
still ceases to pulsate when the stimulus is
applied as above : it does not, however, pre-
sent the dark-red distended appearance, but
is more or less collapsed and pale. The ex-
periment, according to them, seldom or never
fails. If the electric stimulus has been ap-
plied for too long a time the heart again begins
to beat, in the same way as takes place when
the stimulus is applied to the trunk of the
pneumogastric nerve. The same stimulus also
sometimes produces more or less change in
the rhythm of the organ. According to the
Webers, the portion of the central nervous
masses which, when stimulated in this man-
ner, gives rise to a cessation in the action of
the heart, is that extending from the corpora
quadrigemina to the posterior extremity of
the calamus scriptorius. Budge found, in his
experiments, that the corpora quadrigemina
were not so intimately concerned in the pro-
duction of these effects as the medulla ob-
longata. Tiedemann appears to regard the
cerebellum and the medulla oblongata as the
parts through which the cessation of the
heart's action may be induced, while stimulus
applied to the corpora quadrigemina produces
no effect. Valentin believes that while the
corpora quadrigemina and cerebellum exercise
a certain influence, the medulla oblongata is
the part chiefly concerned. In nine mice,
which were rendered insensible by chloroform,
and whose hearts and medulla oblongata were
laid bare, Valentin endeavoured to ascertain
the parts of the central nervous masses which,
when stimulated in the way above mentioned,
give rise to cessation of the heart's action, as
also the effects which are produced by the
same stimulus when applied to the spinal
cord. In none of them did he observe any
* "Weber, "Wagner's Handwbrterbuch, band iii.,
2nd Abtheil, p. 44.
f Ibid. p. 415. &c.
j Lehrbuch der Physiologic, band ii. p. 464.,
et seq.
Midler's Archiv. 1847, p. 498.
462
SYMPATHETIC NERVE.
stoppage of the heart's action when the cere-
bellum, or corpora quadrigemina were the
parts to which the stimulus was applied :
when applied to the medulla oblongata, on
the other hand, this effect was invariably pro-
duced. The cervical part of the spinal cord,
when stimulated, gave different results. In a
mouse, which had been under the influence
of the narcotic for 2 minutes, the heart was
repeatedly made to cease pulsating when the
wires were applied upon either side of the
spinal cord in the region of the third to the
fourth cervical vertebra, and also when ap-
plied to the part between the first and second
cervical vertebras. After repeating this ex-
periment several times, and with the same
result, he cut the spinal cord across in the
region of the second to the third vertebra ;
when the stimulus was now applied to the lower
cut extremity of the cord the heart's action
was accelerated. The cessation produced by
application of the stimulus to this part of the
spinal cord in the former experiment was,
therefore, according to Valentin, probably
due to its being transferred along the spinal
cord to the medulla oblongata. In two other
animals it was found that the two lower
thirds of the cervical portion of the cord in
like manner gave rise to no cessation in the
heart's action, but rather, after the first few
seconds, caused it to be accelerated. A
young rabbit was strangled, the head se-
parated from the body at the articulation
between the occipital and first cervical ver-
tebrae, and artificial respiration kept up. When
the wires of the battery, moderately loaded,
were now applied to the upper part of the
spinal cord, in the region of the first cervical
vertebra, the heart, which was before at
rest, commenced pulsating. The spinal cord
was laid bare from the first cervical to the
eighth thoracic vertebra. When the wires
were inserted in the region of the fifth cer-
vical to the second thoracic vertebra, the
heart's action was distinctly accelerated.
When the spinal cord was removed, the same
result still followed upon application of the
wires, because the roots of the nerves were
stimulated. When the heart was cut out of
the body, and again placed in situ y the above
experiment was repeated without effect.
Just as stimulus of the sympathetic branches
in the mammalia is followed by acceleration
of the heart's action, while stimulus of the
pneumogastric causes it to cease pulsating, so
also Valentin concludes, from the above ex-
periments, that stimulus applied to the spinal
cord gives rise to the former result, while
from stimulus applied to the medulla oblongata
the latter result ensues. In the frog, accord-
ing to Valentin, the spinal cord has no in-
fluence over the movements of the heart. He
also holds, as already stated, that in this
animal, the sympathetic, in like manner, exer-
cises no influence in this respect.
In a pigeon, he found that when the wires
of the magneto-electric apparatus were inserted
into the cerebellum, the heart's action became
more or less laborious : when applied to the
spinal cord, in the reg'on of the first cervical
vertebra, forwards, towards the medulla ob-
longata, the heart's action was repeatedly
brought to a stand.
The cessation in the heart's action by appli-
cation of the galvanic stimulus to the medulla
oblongata most readily ensues, according to
Valentin, when the wires are applied to its
sides, or to the under surface in the vicinity
of the roots of the eighth pair, and in no in-
stance does it ensue when the wires are ap-
plied to any part of the central nervous
masses after removal of the medulla oblongata.
The influence exercised upon the heart's
action by the central nervous masses is also
shown by the diminution in the number as
well as in the strength of its pulsations, which
ensues when these are removed, especially on
removal of the medulla oblongata. That the
diminution in question does not depend en-
tirely upon the stoppage of the respiratory
process consequent on the destruction of the
medulla oblongata, has been shown by Budge.
When, in the frog, the anterior portion of the
medulla is left, the lungs continue to act ; and
yet, according to him, the pulsations of the
heart diminish very rapidly both in strength
and in frequency. He finds that, although
removal of the other parts of the central ner-
vous masses produces little immediate effect on
the heart's action, it seldom continues for any
length of time after the removal of the medulla
oblongata. The effects which follow disease
of these parts in like manner illustrate the in-
fluence which they exercise over the move-
ments of the heart. In compression of the
brain, as well as from lesion of the upper part
of the spinal cord, the pulsations are frequently
diminished : the effects of shock in altogether
stopping its action also illustrate the same
thing.
From the experiments above mentioned,
Valentin and others hold that the nervous
centre upon which the heart's action depends
is the medulla oblongata. The particular
rhythmical order in which its different parts
contract is due, according to some, to pecu-
liarities in the manner in which they are acted
upon by the blood, the contact of arterial with
the lining membrane of the left cavities of the
organ, that of venous blood with the lining
membrane of those of the opposite side, fur-
nishing the proper stimuli, in obedience to
which these parts contract. The successive
contraction of auricles and ventricles is in like
manner explained by the blood first entering
the former, and causing them to contract. By
their contraction it is propelled into the ven-
tricles, and stimulates these to contraction
also, while the contraction of the ventricles
causes the auricles to become again filled with
blood from the veins, and so on indefinitely.
This rhythmical order in the movements of
the organ has also been attributed to pecu-
liarities in the mode of arrangement of its
muscular fibres. The muscular fibres of which
it is composed, as may be seen on examin-
ing with the microscope the auricles in the
heart of the frog or other small animal, do not
SYMPATHETIC NERVE.
463
lie parallel to one another, as in the ordinary
muscles, but cross one another in different di-
rections, many of the bundles being at the
same time observed to present a more or less
branching character. The branches or divi-
sions of one bundle cross those of neighbour-
ing bundles. In this manner the fibres form
a number of reticulated layers laid over one
another, while at the same time bundles pass
from one layer into the adjacent layers, so
that a more or less complete intermixture of
the fibres takes place. The fibres composing the
ventricles also present more or less of this re-
ticulate arrangement. Moreover, many of the
fibres of the auricles pass into those of the
ventricle, and vice versa. In virtue of such an
arrangement of the fibres, stimulus applied to
one part of the heart gives rise to a contrac-
tion in the bundle to which it is applied : since
this crosses neighbouring bundles its con-
traction acts as a stimulus to these, in obe-
dience to which they also contract. In this
manner, the contraction is not limited to the
fibre, or bundle of fibres, to which the stimulus
is first applied, but extends over the entire
mass. So also the contraction of the fibres,
which are described as passing bet ween theauri-
cles and ventricles, stimulate the fibres of which
the latter are composed, giving rise to a ge-
neral contraction in them also ; and in this way
the successive contraction of auricles and
ventricles is produced. According to Schiff,
as mentioned by Valentin, the movements
of the heart may be reduced to the peri-
staltic or vermicular type. He holds that
in a certain part of the muscular substance
are contained the nerves which preside over
the movements of neighbouring bundles.
When this contracts, a stimulus is thereby
given to the nerves which supply the portion
of the muscular substance immediately suc-
ceeding ; so that in this manner a number of
progressive contractions of the successive
bundles of fibres are produced. The contrac-
tion of the auricles or ventricles is thus not a
single simultaneous act ; but is made up of a
great number of contractions succeeding one
another, in the same manner as is seen in the
contraction of the intestine. It is the rapidity
with which they follow one another that gives
rise to the appearance of their being simul-
taneous. These contractions travel from
auricle to ventricle, giving rise to the successive
contractions of these parts. He finds that
when a ring of the muscular substance at the
base of the ventricle in the frog's heart is
brought, by local application of the galvanic
stimulus, into a state of continued or spas-
modic contraction, the due rhythm between
the contraction of the auricles and the part
of the ventricle below the contracted portion
ceases. When a spasmodic contraction is
produced in a part of the ventricle by ex-
ternal stimulus this part may be irritated
without giving rise to any general contraction.
He also finds that when a portion of the
ventricle of a heart which still retains its ir-
ritability, is stimulated, the contraction is
sometimes seen to take place in this before it
takes place in the other portions ; the stimu-
lated portion is also the part which first be-
comes relaxed in the diastole of the organ.
In opposition to the view above mentioned
Volkmann* maintains that the movements of
the heart cannot depend upon the central
nervous masses. It continues its pulsations
after the brain and spinal cord have been
removed. When, however, the rhythmical
movements of a part depend upon a nervous
centre, they cease immediately after the con-
nection between these parts and the nervous
centre is broken. The rhythmical movements
of the muscles of respiration depend upon a
nervous centre, the medulla oblongata. So
soon as this is destroyed they cease. In like
manner the heart, were the medulla oblongata,
or any other part of the central masses of
the nervous system the centre upon which its
movements depend, must also cease pulsating
so soon as it is removed from the influence of
these. According to the experiments of
Bidder, however, already mentioned, frogs
may live for six weeks after the spinal cord
has been destroyed, the circulation, as seen
in the web of the foot, going on as livelily as
before, and presenting no difference when
compared with that in the healthy animal.
So also when the entire central masses of the
nervous system are removed the heart still
continues its pulsations until the second day.
The movements exhibited by the heart, after
the central masses of the nervous system
have been destroyed, cannot, according to
Volkmann, be explained as mere movements
of irritation, due to the inherent irritability
of the muscular fibres, acted on by the
stimulus of the blood or of the atmospheric
air. Mere irritability, acted on by the stimulus
of the blood, or of the air, cannot explain
why both auricles or both ventricles should
contract at one and the same time ; and just
as little can we in this way explain the suc-
cessive contraction of auricles and ventricles.
To explain the rhythmical order in which these
contractions take place it is necessary to sup-
pose that they, like movements of a similar
kind, such as those of the respiratory muscles,
are regulated by a nervous centre. The fact
that the heart's movements continue after it
has been removed from the body indicates,
moreover, that the centre upon which its
movements depend must be contained in the
organ itself. It has been already mentioned
that in different parts of the heart are found
small ganglia. These are believed by Volk-
mann to be the centres on which its move-
ments depend. These, according to him, act
as organs from which the impulse to contrac-
tion proceeds : they are also so connected
with one another as to act in concert, the
impulses proceeding in such directions as to
give rise to the regular succession in which
the contractions of the different parts take
place.
The effects produced upon the heart's
action by stimuli applied to the central masses
of the nervous system, and upon which the
* Loc, cit. p. G16. &c.
SYMPATHETIC NERVE.
view that its movements depend upon these
parts is chiefly founded, are explained by
Volkmann as taking place by reflex action
through the medium of the sympathetic gan-
glia. The fibres which pass from the spinal
cord to the ganglia stand to the proper sym-
pathetic fibres arising in these in the same
relation in which the ordinary sensory fibres
stand to the motor fibres of the muscles of
animal life.
A conclusive way of determining whether
the movements of the heart, as well as the
order in which these take place, depend, or not,
upon the ganglia contained in its substance,
would be to ascertain whether they still con-
tinue after the ganglia have been extirpated.
These, however, are so small, and apparently
so numerous, as to render such an experiment
impossible. That the continuance of these
movements after the brain and spinal cord is
destroyed, as well as when the heart is re-
moved from the body, cannot be attributed to
mere irritability of the muscular fibres acted on
by the stimulus of the blood or of the atmo-
spheric air, but must be connected with
nervous influence, is rendered probable by
several circumstances, but especially by the
observation first made by Henry, and after-
wards by Miiller*, that solution of opium or of
other narcotic substances, when applied to the
outer surface of the heart, does not produce
any obvious alteration in its action, whereas
when introduced into its cavities so as to be
brought into contact with its inner surface,
their almost immediate effect is to cause this
to cease. Again, when stimulus is applied to
one of the ventricles of a heart which has
just ceased pulsating, the contraction thereby
produced does not commence at the point
irritated, as might be expected were the
irritability of the muscular fibres alone con-
cerned, but in the auricles, and is followed
by contraction of the ventricles. Sometimes,
indeed, stimulus applied to the ventricles is
followed by contraction of the auricles alone.
Even when the stimulus is applied to the
apex of the organ, the contraction still com-
mences in the auricles, and sometimes limits
itself to these. The regular order in which
its movements take place, so different from
those produced in the ordinary muscles by
direct application of external stimuli, would
imply that the impulse by which they are
produced must be conveyed in a certain de-
finite direction to the different muscular parts
of which the heart is composed ; and this can
only be supposed to be effected through the
medium of its nerves. The mere arrangement
of the muscular fibres of the heart seems in-
sufficient to account either for the general
contraction of auricles and ventricles or for
the order in which these succeed one another.
Jf, in the case of the heart, the contraction of a
single bundle of the muscular fibres may act as
a stimulus to the neighbouring fibres, by which
they also are excited to contraction, the same
thing ought to take place in the muscles
of animal life : the bundles in these, though
* Muller's Archiv. 1845, p. 423, et seq.
presenting a different arrangement from those
in the heart, are, notwithstanding, in as close
contact with one another as are the latter,
and have equal facility for stimulating the
neighbouring bundles to contraction. The
dependence of the rhythmical movements of
the heart upon a certain arrangement of its
nerves, and moreover that there are certain
portions of the same from which the stimuli
to contraction proceed, is further indicated
by the effects, as shown by Volkmann, which
follow incisions made into the heart's sub-
stance. When a transverse incision is made
through the heart, between its auricles and
ventricles, the former have been found to
continue their contractions much longer than
the latter ; and if a longitudinal incision be
made gradually proceeding from apex to base,
the rhythm is preserved in both portions until
the heart has been divided half way; when
the incision is continued further, however, the
movements of either part become irregular.
When the ventricle is divided transversely into
two portions, that towards the apex either
ceases its contractions immediately or con-
tinues the same only for a short time, whereas
that which is still in connection with the
auricles goes on contracting as before.
It has also been observed that in the heart
of the frog there is one portion of the septum
between the auricles which continues its con-
tractions much longer than any other part ;
and in this portion the greatest number of the
cardiac ganglia and nerves are situated. It
was also observed by Kolliker that the trans-
verse groove in the frog's heart in like manner
exercised a marked influence on its rhythmical
contractions ; and here also the ganglionic
corpuscles and nerves are very abundant. In
young kittens and rabbits also, Valentin has
likewise observed that the groove in question
affects the movements of the heart very much.
The opinion of Volkmann, therefore, that
the rhythmic contractions of the heart are