Gangrene is developed -

1. Out of absolute blood-stasis, which may occur under various circumstances:

(a.) Every hyperemia in organs, or sections of organs, paralyzed or enfeebled, or obnoxious to debilitating influences, may degenerate into absolute stasis. This applies particularly to asthenic, hypostatic hyperemia in torpid peripherous organs, vegetating, so to say, imperfectly under the embarrassment of continued pressure.

(b.) Mechanical hyperaemia frequently becomes absolute stasis, as observed in incarcerated, strangulated organs, and as a consequence of extensive plugging of the returning vessels in the lower extremities.

(c.) Every inflammatory stasis may degenerate into absolute stasis, more particularly those hypostatic and asthenic inflammations which occur in organs already diseased, paralyzed, or depressed by violent external influences, such as concussion, contusion, cold, or heat. An inflammation consequent upon influences directly or indirectly debilitating, may acquire, during its progress, a tendency to absolute stasis.

In absolute stasis, the blood undergoes gangrenous decomposition. Hence the blood is the portion originally necrosed and dissolved. It exudes in a state of gangrenous decomposition, and in the form of ichor, through the walls of bloodvessels, engendering the same gangrenous decomposition both in these and in the surrounding textures. This event gives rise to the most ordinary and most developed form of moist gangrene, in which the textures are, through the medium of the blood, broken down to a dark-colored, friable and lacerable, diffluent, and highly fetid pulp. The dark discoloration, however, of gangrene thus developed, is subject to various modifications due to certain elementary products, which the inflammatory stasis has generated both within the bloodvessels and without.

The progress of this gangrene is more or less acute, the gangrenous dissolution of tissues, already referred to under the term putrescence, being particularly marked by the rapidity of its course.

2. Gangrene is determined by failure in the supply of blood:

(a.) In impermeability of large arteries, - high degree of coarctation, and complete obstruction - consequent upon arteritis and ossification.

Here the gangrene, for the most part, takes the form of comparatively dry, black, mummifying gangrene.

(b.) As the result of the immediate compression and tension of a part; for instance, in incarcerated hernia.

(c.) As a consequence of the local destruction of bloodvessels, the denudation of parts of attaching and blood-supplying textures, - bones, for example, of their external and internal periosteum; the common integuments, of their supporting areolar tissue; the peritoneum, of its subjacent layers; isolation of the pulmonary pleura over cavities of the lung.

The gangrene appears as a white or yellowish-white slough.

To this category belongs the necrosis of smaller textural parts, loosened mechanically by exudation or by ulceration.

(d.) Extensive impermeability of the capillaries and minute vessels when plugged with coagula, or compressed by surrounding exudates.

In the last-mentioned case, the gangrene is dependent upon inflammation. To this kind of gangrene, textures poor in bloodvessels, such as compact bones, callosities, etc, are especially obnoxious. The color of the necrosed textures differs with the different nature of the coagulation, and of its exudate. Answering to the croupous character of bulky exudates, the textures involved in the necrosis commonly assume a yellow or yellowish-green hue.

3. The gangrene is the expression) the localization of an anomaly in the blood-erase, either directly ingrafted by infection (contagion), or developed out of other crases; a putrid decomposition of the circulating fluid. Blood so poisoned, especially if brought into stasis or into coagulation, possesses, in common with the exudates thrown out by it, an inherent tendency to gangrenous dissolution.

It has been already stated, that several varieties of gangrene are recognized:

1. Gangrene Developed Out Of An Internal Cause

Gangrene Developed Out Of An Internal Cause is distinguished, by the designation of primary gangrene, from that arising out of a predominant external cause.

2. Hot, Acute, Inflammatory Gangrene True Gangrene

In what wise inflammation leads to gangrene, is sufficiently clear from the foregoing.

(a.) The inflammatory stasis, owing to its very intensity, to pre-existent debility of the diseased textures, or, lastly, to weakening influences exercised during its progress, degenerates into absolute stasis.

(b.) It occasions gangrene by the crushing effect of its products upon the capillaries, or by the mechanical or ulcerous isolation of textural parts.

In the first case, the necrosis affects more immediately the blood held in stasis; in the second, the textures. In the first case the gangrene is, as it were, an immediate issue of the inflammation, the opposite to resolution; in the second it is a remote consequence thereof.

In this way, gangrene may arise in tissues laboring under the sequelae of inflammation, without being itself an issue of the latter.

3. Cold Gangrene, Sphacelus

Cold Gangrene, Sphacelus, is so-called, as being unconnected with inflammation.

4. Moist Gangrene

Moist Gangrene comprises the breaking down of fluid substances to gangrenous ichor, and of fibrin textures to a variously discolored, diffluent pulp, marked by its evolution of fetid gases. It is the gangrene developed out of absolute blood-stasis; - therefore, again, inflammatory gangrene. It may be compared to the decomposition of animal matter under the co-operating influence of water.

5. Dry Gangrene

Dry Gangrene is a consequence of deficient blood supply. It manifests itself in the perishing of the implicated textures, with shrivelling or withering thereof, to an incipiently tough, but eventually sloughing mass. Often, and particularly in the gangrene termed senile, which affects the extremities, especially the inferior, owing to impermeability of their arteries, the gangrenous textures blacken; wherefore this species has been designated as mummifying gangrene. As such, it is comparable to the decaying of organic matter, that is, to decomposition with absence or insufficiency of moisture, and with the disengaging of pure carbon. Dry gangrene is frequently called gangrenous slough.

6. Black Gangrene

Black Gangrene, gangrenous slough.

7. White Gangrene

White Gangrene, gangrenous slough, occurs, for the most part, as a consequence of pressure in incarceration; of the denuding of membranous expansions of their subjacent textures, for example, as peritoneal sloughing at the base of intestinal ulcers. Again, it is generated by the necrosis or death of textures replete with fibrino-croupous exudates, or of such coagulate exudations themselves. This refers more particularly to the common integuments, the mucous membranes, fibrous and areolar tissue expansions upon wounded and ulcerated surfaces. To this head belongs hospital gangrene.

Of these different species of gangrene, several are often concurrently present. Beneath the common integument, often transformed into a swarthy parched rind, in senile gangrene, we frequently meet with patches in which the textures are reduced to a humid stinking pulp.

Just as gangrene of the solids, gangrenous slough, varies, so in like manner does gangrenous ichor, as necrosed blood or exudate vary, according to the crasis or constitution under which either has become attacked with gangrene. Thus the necrosis of typhous blood differs from that of pus-blood, or of fibrino-croupous blood.

Like normal textures, - diseased textures and new growths, fibroid, cancerous formations, for example, may become a prey to gangrene. Neither to ulceration nor to gangrene are all textures alike obnoxious. Bony, elastic, fibrous textures resist gangrene more ably than muscle, areolar tissue, or mucous membranes. Lax embryonic textures, as, for instance, certain kinds of cancer, are especially prone to gangrenous destruction.

The constituent elements of gangrenous texture-masses are, more or less well-preserved textural debris, larger or smaller black-contoured molecules down to a pulverulent granule mass, black and brown pigment granules, fat-drops and crystals, saline crystals.

Contact, reciprocity of action, with the atmosphere, is by no means indispensable to the generation of gangrene. It affects equally with the external parts, organs never in contact with the air, as the liver and the spleen.

A very important phenomenon involving a curative act, is the circumscription of gangrene by an inflammatory process of ulceration, - isolation of the gangrenous part through its own secretion. The ultimate healing is brought about by the same inflammatory process changing to one of pus-production, and of regeneration.