As nearly all inflammations have significant exudations it is well to
follow these in their subsequent progress through reabsorption and
removal, development into new tissues, necrosis, suppuration and
ulceration.
=Resolution.= If an inflammation, slight in character and with only a
moderate exudation, subsides and is followed by a rapid liquefaction of
the cells and fibrinous coagula and a reabsorption of the exudate, so as
to leave the part in its primary healthy condition structurally and
functionally, it is said to have terminated by “_resolution_.” If this
occurs with extraordinary rapidity it is said to have ended by
“_delitescence_.” This is not always an unalloyed good, as often in
delitescence, coagula and infecting material may be carried on by the
circulation, to block the next set of capillaries in its course and set
up new centres of inflammation. This is one form of “_metastasis_”
though a more definite _metastasis_ is in rheumatism where the disease
attacks one joint today and a distant one to-morrow.
=Inflammatory New Formations.= Of the growths in lymph there are two
principal kinds: first, _the plastic_, _fibrinous_, _granular_ or
_molecular_; and second, _the aplastic_ or _corpuscular_. The first form
tends to develop into new structure, the second to disintegrate and
decay. The tendency to one or other form depends largely on the strength
or weakness of the system’s health, on the deficiency or excess of
corpuscles in the exuded fluid, and on the distance of the latter from
living tissues and blood supply. Much also depends on the predisposition
of the genus, the tendency to suppuration in lymph being in a descending
series from horse, ass, and mule, through ox and sheep, to dog, pig, and
finally, the bird, in which latter suppuration is quite exceptional.
=Suppuration.= In inflammations of a high type, in those occurring on
the skin or mucous membranes in which there is an extraordinary increase
of nuclei and embryonal cells, and in lymph thrown out in excess at one
point, so that its central parts are far from vascular tissue and
nourishment, the cell elements undergo a rapid increase and degradation
into pus-corpuscles, and its solidified intercellular lymph undergoes
granular decay and liquefaction into pus.
While the above conditions are favorable to the formation of pus, the
process of suppuration must now be recognized as an infective process
due to the propogation of bacteria (mainly chain forms—_Streptococcus
pyogenes_—cluster groups—_Staphylococcus py__ogenes_—and rod
forms—_Bacillus pyogenes_). These or other bacteria are found in the pus
of acute abscesses, and when absent in chronic abscesses are to be
considered as having perished since the abscess was recent and active.
Inoculation of a rabbit with an excess of the pus of an acute abscess
produces general purulent infection (pyæmia) and early death; from a
medium dose an abscess is produced; while from a small dose there is no
effect whatever. In the latter case the bacteria are overcome and
devoured by the abundance of vitally potent white blood globules and
tissue cells. This pus-forming action of these bacteria explains the
great difference in results in wounds exposed to the air and those in
the interior of the body and far removed from air and its floating
bacteria. A broken bone, with no wound in the skin and little injury to
parts around the fracture, is readily repaired without any formation of
pus, if merely kept still and immovable; whereas a broken bone,
continuous with a wound through the skin, always tends to form pus or
become otherwise infected, and is extremely dangerous even to life. The
tendency of every open sore is to form pus on its surface but this may
be arrested and avoided by preventing the access of germs, or by a free
use of disinfectants and a covering which shall arrest and filter out
the germs. Similarly in an abscess, evacuation followed by the injection
of disinfectants, without the formation of any perceptible permanent
opening to the outer air, will put a stop to the pus-formation. The
subjection of an inflamed part to the control of these pus-forming
bacteria is dependent on the lowered vitality and power of resistance of
the inflamed tissues, and of the white cells of their circulating blood.
Healthy parts can successfully resist them, though they are constantly
present in surrounding air and on objects, but in this as in all other
cases, of bacterial infection, so soon as the tissue is injured,
inflamed and lowered in its power of vital resistance, the pyogenic
bacteria assail it successfully. Hence, too, the more abundant
exudations of lymph, the centres of which are farthest removed from the
healthy tissues and from nourishment, are the most prone to suppuration.
That the germs can make their way to such deep-seated exudations in the
substance of solid tissues is to be accounted for by their gradual
advance through the inflamed and weakened structures from the adjacent
skin or mucous membrane, or in some instances by reason of their
presence in small numbers in the blood. It is further noteworthy that
those animals in which suppuration does not occur readily are such as
have a special power of resistance to some other organic poisons. Thus
the hog, which is supposed to be proof against snake-bite, is also, to a
large extent, proof against the pus-forming bacteria.
=Pus.= This is a white, or yellowish white, creamy-looking product,
composed of a clear, transparent fluid, rendered opaque by numerous
floating pus-corpuscles. These pus-corpuscles have the same size as the
white globules of the blood (¹⁄₂₅₀₀ to ¹⁄₃₀₀₀ inch) and are peculiar in
that each shows within it three or more nuclei, which become visible on
the addition of a drop of water or acetic acid. Each of the common
embryonal cells found in the inflamed tissue usually contains two
nuclei, the indication of the active increase by division into two, but
when the supply of nutriment is checked the nuclei continue to divide,
while the cells remain unchanged, and thus every cell comes to contain
several nuclei in addition to fatty granules, and constitute
pus-corpuscles.
When pus is formed in a well-maintained system and tissue, the outer
layer of the lymph is developed into a fibrous sac enclosing the liquid
pus and constituting an _abscess_. In an unhealthy system, or when the
inflammation depends on some injurious poison, like that of erysipelas,
this sac may not be formed, and the pus, burrowing into and between
different organs, destroys the connections and substance—_diffuse
suppuration_. When an abscess has formed in soft tissues its investing
sac shrinks as it assumes the fibrous character, and the confined pus
being incapable of compression, presses the membrane outward on the side
in which the surrounding tissues are most loose and least resistant,
hence, usually, though not always, in the direction of the skin; the
soft tissues become absorbed and removed in the track of the advancing
pus; and, finally, the latter reaches a free surface and escapes. Thus,
an abscess usually bursts through the skin, but also, at times, through
a mucous membrane into the lungs, bowels, etc., or through a serous
membrane into chest, abdomen, etc. When an abscess is formed in bone or
dense fibrous tissues which press equally on all sides, it may remain
imprisoned for months and years after all inflammation has subsided,
constituting an _indolent_ or _cold abscess_. When the imprisoned pus is
inclosed by thick fibrous or resistant tissues at all points but one, it
will make its way along the narrow passage of yielding tissue, but as
the resulting outlet is constricted, long, and tortuous, the contents
cannot readily escape through it nor the walls of the abscess contract
so as to expel the confined pus, and the latter goes on forming and
discharging through the narrow outlet for months or years. This is a
_fistula_ or _sinus_.
=Healing by Adhesion or First Intention=. When a clean-cut wound has the
blood staunched and its lips brought together without exposure to the
air (or contact with pyogenic germs), they adhere at once and heal
without pus or almost any appreciable formation of new tissue. Here the
lymph thrown out on the cut surfaces agglutinates them, and the cells,
multiplying, form a thin layer of embryonic tissue which gradually
develops into a fibrous structure and repairs the breach without any
perceptible scar.
=Healing by Second Intention. Granulation.= When a wound has caused
destruction of tissue, or when a simple incision is left exposed to the
air, the breach is filled up by new tissue through the process known as
granulation. The superficial layer of lymph thrown out on the raw
surface becomes oxidized and degenerates into pus, while the deeper
layers become solid, fibrillated, the seat of cell growth, and are
finally transformed into a fibrous structure. New bloodvessels form in
loops in the developing lymph and constitute the bright red
granulation-points which cover the raw surface. The fibrous tissue into
which the lymph is transformed undergoes gradual contraction in
development, and thus, day by day, the edges of the adjacent healthy
skin are drawn in, so as to cover the wound more or less perfectly, and
a slight scar only is left when healing has been accomplished.
=Granule Corpuscles and Masses.= This is another degenerative
transformation in lymph and, is seen mainly in inflamed glands and brain
and lung tissue. The cells found in the exuded lymph are made up of
granules ¹⁄₁₀₀₀₀ inch in diameter, and besides these, large, irregularly
shaped masses of granules are extended along the capillary bloodvessels.
After the lymph has coagulated these granular masses soften and liquefy
preliminary to reabsorption and removal, and the restoration of the
tissue to a healthy condition. When in excess this softens and
disintegrates the tissues, leading to permanent loss of substance. See
_granular_ degeneration.
=Interstitial Development of Lymph into Tissue.= This is equivalent to
what takes place in the formation of the sac of the abscess or of
granulation-tissue. The liquid lymph in coagulating, becomes fibrillar,
and the cells and nuclei of the adjacent tissue, having an abundant
supply of blood and nutriment, multiply first as simple, rounded
embryonic cells, then deposit around them new tissue, becoming
elongated, spindle-shaped, branching, etc., and thus get imbedded in a
fibrous material of their own formation. These new formations are
usually of a low type of organization, like white fibrous tissue or
bone, and hence, although breaches in the higher structures like muscle,
nerve, gland, skill, are filled up, it is usually only by the drawing
together of the remaining healthy parts by these new formations without
the restoration of any of the original tissue which has been destroyed.
The cicatrix (scar), alone is made up of new material.
Lymph developing in this way may undergo any degeneration to which
normal tissues are subject. Thus it may undergo black pigmentary
(_melanotic_) degeneration, it may become impregnated with lime-salts
(_calcified_), it may wither up into a hard _gelatiniform_ or _horny_
mass, or it may undergo _fatty_ degeneration.
=Fatty degeneration= is the most common form, and consists in the
excessive deposit of fatty granules, first in the cells which are in
excess or badly nourished, and next in the adjacent tissue, the normal
elements of which are replaced by fatty granules.
=Softening= is an almost constant result of inflammation. The exudate
infiltrates and separates the tissue elements, destroying their
cohesion; the liquefaction of these elements impairs this still further,
and the more or less perfect transformation of the tissue into embryonic
tissue entails the loss of its rigidity and power of resistance. Thus
the inflamed brain-tissue may become a mere pulp, and the inflamed bone
may be cut with a knife.
=Ulceration= is closely allied to softening. On the surface of a sore
there is an excessive exudation of lymph, which loosens and
disintegrates the layer of lymph that is already in process of
development, and also a part of the tissue beneath. The cells in these
parts fail to develop naturally and to build up good tissue; they become
fatty, die, and together with the tissue in which they lie, break down
and pass off as a pulpy debris. Thus the sore constantly deepens and
widens, or at least refuses to contract and heal. It is usually the
result of bacterial infection.
=Gangrene= or =death of a part= is another effect of inflammation. It
results usually from the cutting off of the blood supply through the
obstruction of the bloodvessels; by the pressure of excessive exudation
in unyielding structures, as in bone, or under the hoof; by implication
of the inner coats of the bloodvessels in the inflammation, when the
contained blood will clot and obstruct them; or by blocking with the
blood clots that have been formed at a distance and washed on in the
blood current to be arrested when they reach vessels too small to admit
them. Like suppuration, gangrene is associated with and often caused by
a bacterial growth. The dead mass remains as an irritant, and is slowly
separated by the formation around it of embryonal tissue, granulations
and pus. A second form is _molecular gangrene_, in which the cells and
minute elements of the tissue die, and are cast off, leading to
phagedenic (eating, extending) sores, as noted above under Ulceration.
When gangrene occurs on an exposed surface, that may be altered from the
normal color into shades of yellow, brown, green, red, or black,
according to the amount of blood and the stage of decomposition, and may
be cut without pain, if the subjacent parts are not pressed upon; it may
be soft, may pit on pressure, may crackle under the hand from the
evolved gases of decomposition, and may be covered with blisters
(_phlyctenæ_) with red, grumous liquid contents (_moist gangrene_);
again, it may be white, as after freezing, or it may be dark colored,
dry, and horny, as from ergotism (_dry gangrene_).