It has been asserted by _Bichat_[11] that the immediate cause of death,
when it takes place suddenly, must be the cessation of the functions of
the heart, brain, or lungs; although it is sometimes difficult to
determine which of these organs is the first to fail in its action; this
may be well exemplified by the poisonous operation of Arsenic upon the
animal economy, which when introduced into the circulating system will,
according to the valuable experiments of _Mr. Brodie_, occasion stupor
and paralysis, a feeble and intermitting contraction of the heart, and
slow and laborious respiration; but it is found that in some cases, one
order of symptoms will predominate, and be the first to display
themselves, whilst in others, the very contrary will obtain, without
perhaps our being able to assign the immediate cause of such deviations.
There are, moreover, cases of sudden death, in which the principle of
animation would seem to be at once annihilated in every part of the
animal machine, and when every organ appears to be simultaneously
affected, as in that occasioned by the agency of intense cold, and
sometimes, for it is not in every instance, by that of lightning, or
electricity; still, as a general proposition, the aphorism of _Bichat_
must be admitted; and we shall proceed to investigate the subject of
sudden death, as connected with medico-judicial inquiry, upon principles
deduced from the enlightened views of this distinguished philosopher. To
the able and satisfactory researches of our English physiologist, _Mr.
Brodie_, we are also greatly indebted for a correct notion of the nature
and order of succession, of those events by which life is quickly
extinguished; his attention was many years ago directed to one important
branch of this subject,—to the investigation of that series of changes
produced on living bodies by the operation of poisons, the results of
which were published in the _Philosophical Transactions_,[12] to which
we shall have frequent occasion to refer in the following pages. Since
that period he has diligently pursued the subject in its more extensive
ramifications, and in his lectures, delivered from the anatomical chair
of the College of Surgeons during the last year, he presented a
condensed and philosophical history of the phenomena of death, in
general, in which he elucidated many leading points that were before
obscure, established several propositions that have long been considered
doubtful, and rejected a mass of popular error, which, under the
sanction of authority, has continued to retard our inquiries, and to
embarrass and misguide our practice. The author of the present section
of this work has to acknowledge the kindness and liberality by which he
is enabled to avail himself of these luminous researches, having been
furnished by his friend _Mr. Brodie_ with the manuscript notes from
which the lectures were delivered.
The organs more immediately necessary to life are, the HEART, which
conveys to every part of the body that fluid, without a constant supply
and change of which, vitality must be speedily exhausted; and the LUNGS,
by whose functions this essential fluid undergoes those unknown changes,
from the action of the atmosphere, which adapt it for the performance of
the important duties to which we have alluded.
In conformity with these views, the functions of the heart, and their
connection with those of the lungs and brain, very naturally present
themselves as the first objects of physiological inquiry; and there is
certainly no discovery in modern times more interesting in its
relations, and at the same time so useful in practical application, as
that which has determined the nature of the connections between the
functions of respiration and the motions of the heart; and shewn why the
cessation of the former should occasion the destruction of the latter.
The existence of this mysterious connection constituted a subject of
interest and inquiry in the more remote ages, and it will not be
unprofitable to take a review of the different theories which have been
proposed for its explanation. Until the celebrated experiment[13] of
_Hook_, it was supposed that the heart’s motion was maintained by the
alternate contraction and dilatation of the lungs in the act of
breathing; but the extraordinary philosopher above mentioned decided
this point by exposing the thorax of a dog, and separating the pleura
extensively from the external surface of the lungs, and then, by means
of a pair of double bellows, keeping up a constant stream of air through
the air cells; by this contrivance respiration was duly performed, while
the lungs remained motionless, and yet it was found that the vigour of
the heart’s action was not in the least impaired; whereas, if the theory
which _Hook_ undertook to refute, had been founded in truth, the heart,
under such circumstances, must necessarily have become quiescent. _Mr.
Hunter_[14] supposed the existence of a sympathy, or association,
between the motions of the heart and lungs; and the same opinion appears
to have been entertained by _Dr. Currie_[15]; _Dr. Darwin_[16] deduced
the existence of this immediate connection from that general law of the
animal œconomy, by which motions that are frequently repeated in
succession acquire the power of recurring in the same order,
independently of the original exciting cause; “it is thus,” says he,
“that by the stimulus of the blood in the right chamber of the heart the
lungs are induced to expand themselves.” _Dr. Bostock_[17], however, has
very satisfactorily opposed this hypothesis, by observing that in the
fœtus the heart commences its contractions immediately upon its
formation, while the lungs remain perfectly at rest; and that when the
animal leaves the uterus, the motion of the lungs commences, but the
periods of the contraction of the diaphragm bear no determinate ratio to
those of the systole of the heart.
It was long supposed that the cessation of respiration occasioned that
of the heart’s motion, in consequence of the black blood not having
sufficient power to stimulate its fibres; but does not the right side of
the heart, which, under all circumstances, contains de-oxygenated blood,
contract with a vigour equal to that of the left? It was reserved for
_Bichat_ to offer a true explanation of this phenomenon; he has very
justly stated that, in consequence of the suspension of the respiratory
function, the coronary vessels, by which the muscular structure of the
heart is supplied, are compelled to carry black, instead of scarlet
blood; a fact which in itself is quite adequate to explain the cause of
the heart ceasing to contract; for the irritability of this, like that
of every other muscle, can be alone maintained by duly oxygenized blood.
But it remains to be shewn how the functions of the brain and nervous
system stand related to those of the heart and lungs. Although the
agency of nervous influence is necessarily involved in impenetrable
obscurity, yet we shall not have much difficulty in proving, that _the
brain_[18] _is immediately necessary to life only because the muscles of
respiration owe their action to its influence_. _M. Lallemand_ has
published the history of a fœtus, in which the brain and spinal marrow
were equally deficient, notwithstanding which, it even exceeded the
usual size, the heart was perfect, and it was evident that the
circulation had been properly performed; no sooner, however, was the
monster born than it perished, because the diaphragm and other muscles
of respiration were unable to perform their functions without the aid of
nervous excitement; no air was therefore inhaled into the lungs, and in
a few minutes the heart ceased to contract from the deficient supply of
oxygenized blood. If the phrenic nerves of a quadruped be divided,[19]
the motion of the diaphragm ceases, and the animal breathes by the
motion of the ribs alone, panting and respiring with difficulty and
distress. If the spinal marrow be divided below the origin of the
phrenic nerves in the lower part of the neck, no interruption is given
to the transmission of the nervous influence to the diaphragm, but the
ribs now become motionless, and respiration is performed by the
diaphragm only; if the spinal marrow be divided in the upper part of the
neck, above the origin of the phrenic nerves, the nervous influence is
neither transmitted to the diaphragm, nor to the muscles which produce
the motion of the ribs, and respiration is entirely suspended; under
these circumstances the heart continues to contract for some minutes,
after which it ceases, as there is no supply of blood which has received
the influence of the air, and, consequently, the muscular fibres of the
heart lose their excitability, and the blood is no longer circulated;
if, however, the lungs be artificially inflated, before the action of
the heart has ceased, its motions are continued. The experiment may also
be very satisfactorily varied in the following manner; apply a ligature
to the carotid arteries in the neck, so as to prevent the occurrence of
hemorrhage, and then decapitate the animal; if respiration be now
artificially maintained, the heart will suffer no disturbance in its
motions, but the circulation will be preserved for several hours in the
body of the decapitated animal. In further illustration of this view of
the subject, _Mr. Brodie_ observes, that many reptiles which are capable
of respiring by means of the skin, will survive the loss of the brain
for so long a period, that the wound made by decapitation, becomes
cicatrized, and death only takes place at last in consequence of
inanition.—(_Manuscript Notes._)
In farther illustration of these views, let us observe the mode in which
death takes place in apoplexy, or in cases of pressure on the brain,
whether occasioned by a depressed portion of bone, or by blood
extravasated within the cranium. At first the patient is insensible to
all external impressions, but the breathing is not affected; after an
interval, however, the respiration becomes difficult and laborious, and
the purple hue of the lips and cheeks, from the sub-cutaneous vessels,
demonstrates that the blood is imperfectly oxygenized. The arterial
action becomes more slow, in proportion only as the respiration is more
difficult; and the pulse may even be distinguished at the wrist, after
the breathing has altogether ceased; under such circumstances it is
obvious that life might be protracted for several hours by artificial
inflation of the lungs, but as no ultimate benefit could be derived from
such an operation, its expediency may be fairly questioned.
Enough has been said to shew that the brain is not _immediately_
necessary to the action of the heart; but _Mr. Brodie_ has very justly
observed that the general proposition thus established, must not lead us
to the conclusion that the heart is therefore incapable of being
affected by violent impressions on the nervous system; the fact is quite
otherwise, for although the brain may be removed, and the circulation be
nevertheless maintained by artificial respiration, yet an injury
inflicted on the brain, of another kind, may be followed by those
immediately fatal consequences which decapitation itself would not
produce. _Dr. Wilson Philip_ states that if the brain be violently
crushed, the action of the heart is immediately stopped; and the fact is
too notorious to be questioned, that a blow on the head is frequently
succeeded by Syncope; there are but few circumstances, says _Mr.
Brodie_, in the history of the animal œconomy which appears more
remarkable than this fact, that _an injury of a part which is not
immediately essential to the heart’s action, should nevertheless, under
certain circumstances, have the effect of occasioning its immediate
cessation_. The late researches of _Le Gallois_ may perhaps receive
farther elucidation from the above proposition; this physiologist has
stated that if a wire be introduced into the _Theca vertebralis_, and be
moved upward and downward, so as to destroy the texture of the spinal
marrow, the action of the heart presently ceases; and he from thence
advances to the conclusion, not only that the spinal marrow is necessary
to the heart’s action, but that every part of the animal body derives
its vital properties from it; from what I have observed, says _Mr.
Brodie_ (_Manuscript Notes_) in the repetition of the foregoing
experiment, I should infer that the fact is correctly stated, as far as
it relates to warm-blooded animals, but the conclusions are undoubtedly
premature; and the history of the fœtus, as related by _Lallemand_, in
which, notwithstanding the absence of the brain and spinal marrow, the
child was even larger than usual, the heart perfect, and it was manifest
that the circution had been duly performed, is in direct opposition to
such a theory. We must here agree with _Mr. Brodie_, that such phenomena
are quite incompatible with the doctrine in which the spinal marrow is
supposed to be directly necessary to the existence of vitality in the
system generally, and to the action of the heart in particular; and that
we must therefore look for some other explanation of the effects which
are produced by the destruction of the spinal marrow in warm-blooded
quadrupeds.—May they not be explained by supposing them to be the effect
of the shock which must necessarily attend the removal of the spinal
marrow, which can never be effected with the facility that attends
decapitation?
We have deemed it necessary to offer these few remarks upon the
relations which subsist between the functions of the heart, lungs, and
brain, in as much as the propositions which have been thus established
respecting them, can alone lead to a correct pathology of those
diseases, by which life is suddenly extinguished, or suggest a rational
and effectual plan of treatment, in cases of suspended animation.