Sometimes during life, some portion of the body is in a condition of
gangrene, that is, the tissues are not only dead, but decomposing.
With the evolution of gases, the softening and liquefaction of the
solid parts, and the development of minute organisms, either animal
or vegetable.
The bodies of persons who have died from such causes, _decompose
with unusual rapidity_. The inner coats of the vessels are often
stained with the coloring matter of the blood. The viscera are soft
and flabby, the stomach may be swollen, and the kidneys congested and
degenerated.
People who have suppurating wounds or abscesses may, without much
change in the wounds or abscesses, be seized with rigors followed by
fever, become jaundiced and die.
In such persons after death, the same tendency to rapid
decomposition, and all the symptoms of the preceding cases are to be
found.
There is no way of accounting for the rapid decay in the preceding
cases, except by supposing that the pus from the original wound or
abscess in some way infects the system, and renders the tissues prone
to putrefy.
There is another modified condition of the body very different
from the two preceding. Either in consequence of wounds, injuries,
inflammations, abnormal conditions of the system, or changes in the
venous walls, the blood may become coagulated during life and form
thrombi in the veins.
These thrombi may become organized, or they may soften, break
down, and their fragments be carried into the circulation; by
their mechanical action in obstructing the vessels, they produce
extravasation of blood.
By the irritative character of the thrombi themselves, they excite
inflammatory action in the adjoining tissues; in this way are
produced multiple abscesses. Therefore, we find in persons who die
under such conditions, abscesses in the brain, heart, lungs, kidneys
and intestines; further we may find purulent inflammation and
abscesses in the connective tissues.
It is now necessary to explain the nature and composition of both the
thrombus and embolus, and how, through their mechanical agency, the
process of embalming may become seriously impaired, if not altogether
arrested. A thrombus is a clot, composed principally of the fibrine
of the blood, formed during life in the cavities of the heart, the
arteries, the veins, or the capillaries.
An embolus is a solid body, usually a portion of a thrombus, carried
by the blood current into some artery or capillary, and becomes fixed
there. A thrombus may entirely fill the cavity of a vessel, or it
may only form a layer on its wall, or it may project from a smaller
vessel into a larger one.
An embolus may completely or only partly plug up a vessel; it may
remain alone or a thrombus may be formed around it.
A thrombus may merely become harder and whiter in time, or it may
become organized, or it may degenerate, soften, and change into a
mass of puriform fluid and _gangrenous looking fibrine_, or it may
calcify.
The production of thrombi is due to various causes.
(1.) Spontaneous thrombi are produced by any cause which seriously
weakens the whole system, as old age and chronic exhaustive diseases.
They are usually formed in the veins of the lower limbs and pelvis,
and in the sinuses of the dura mater.
(2.) Compression of the vessels by ligatures, tumors, dislocated
bones, and inflammatory exudation. _Pneumonia_ may produce
_thrombosis_ of the _pulmonary veins_. _Phthisis_ may produce
_thrombosis_ of the _pulmonary arteries_.
(3.) Thrombi may form into capillaries or small veins, and increase
until they project into larger veins.
(4.) It may also form when there is inflammation, especially of a
gangrenous and suppurative nature, in the parts around a vessel.
The causes of embolism are also various.
(1.) Fragments of thrombi in the veins are the most frequent material
of emboli.
(2.) Thrombi of the heart, vegetations on the valves and on the walls
of the aorta.
(3.) Portions of the inner-coat of the aorta may become detached and
form an embolus; also portions of tumors which project in the veins,
and fat may form emboli.
In a considerable number of cases, it is impossible to find any
source for embolus. It must be remembered, however, in emboli, in
connection with wounds, that not only the veins of the wounded region
are to be examined, but also those of the pelvis.
The consequences of thrombosis vary with the situation of the clot;
thrombi in the arteries produce either a lack of circulation in the
region supplied by the artery, or else intense congestion from the
collateral circulation. Later there may be inflammatory changes,
softening, or gangrene. Thrombi in the veins produce inflammation in
and around the vein, thickening of the skin and connective tissue,
gangrene and hemorrhage.
The consequences of embolism vary with the character of the embolus
and its situation. A simple plug of fibrine in a vessel only produces
changes in the circulation, but a plug from a gangrenous thrombus has
a tendency to excite suppurative inflammation wherever it lodges.
The size of the artery thus obstructed, and the character of its
collateral circulation also lead to a variety of results. If a large
artery is stopped, the part becomes empty; if a small one the part
may become extravasated with blood from the collateral circulation.
Thus, if the large arteries supplying the extremities are obstructed,
paralysis of the muscles, and finally dry gangrene, ensue.
Emboli of the pulmonary arteries produce sudden death; of the
coronary arteries, sudden death; of the cerebral arteries, softening
of the brain; of the retina, sudden blindness; of the mesenteric
arteries, congestion and gangrene of the intestines.
Abscesses are also produced. This takes place when the embolus is
of an irritative and gangrenous nature. Large abscesses are only
found in the lungs and liver, therefore the mechanical results of an
embolus produce the following condition of affairs: A set of vessels
are first emptied of their blood, and the nutrition of their walls
thus impaired; after a time these vessels are filled up from the
veins, their abnormal walls can no longer resist the blood pressure,
and hemorrhage takes place.
After an hemorrhagic infraction is formed, the subsequent changes
are of a degenerative character. The blood loses its coloring matter
and breaks down into a mass of granules, forming a dry, yellow,
wedge-shaped mass, or it may break down and form into a puriform
fluid, or it may be surrounded by a zone of inflammation or of
gangrene.
The above condition of the system will explain why and under the
circumstances enumerated, the injection of a blood vessel may
be brought to a sudden stop without any apparent cause, and the
injecting fluid flow back towards the injecting point.
The various causes for such a result have been clearly demonstrated,
but with the knowledge of these causes as previous stated, the remedy
can be applied without much trouble. It can be estimated by the
amount of fluid injected, about to what extent the vessel has been
filled, and by following its course the point where the obstruction
is, can be easily ascertained.
By reopening the vessel at a point above, the injection may still be
carried on successfully, or the corresponding vessel on the other
side of the body may be used for that purpose.
It is then that even a limited amount of knowledge of anatomy of
the human body will be found of immense advantage to the operator,
inasmuch as it will trace the cause of action, to be followed in this
case, and will enable him to do so with success.
If, on the other hand, too great a pressure is brought to bear, so as
to remove the obstruction by the mere weight of the fluid injected,
the walls of the vessel may not be able to resist the strain, and the
injecting fluid loses itself in the surrounding tissue and cavities,
thereby failing to accomplish its mission.