In a few cases this mode of termination has been found throughout the whole of a large muscle, and even in all the muscles of one or more of the limbs, particularly of the lower extremities: they were changed into a white tendinous structure, and here and there into bone.

Osseous substance may be developed at a later period in the fibroid callus (ossification); and, in a few cases, it has been seen occupying entire muscles.

It happens, but very rarely, that induration of the muscular coat of an organ may be traced to a chronic inflammatory process. I have met with one such instance in the muscular coat of the bladder. It was changed into a pretty thick and firm lamina, of a uniform pale red color, inclining to yellow: the original bundles of muscular fibre had disappeared. It was closely united with the mucous membrane, but presented none of the peculiar change of texture characteristic of cancerous degeneration. The bladder was paralyzed and distended.

When inflammation of muscle terminates in suppuration, the matter may be formed at one or at several isolated spots; or if the process be extensive, rapid, and violent (tumultuous), it may involve the whole of the muscle at once. The abscess commences with the deposition of matter at several points; the intermediate muscular fibre becomes pale, or in some way discolored, and is dissolved; the points of matter coalesce, and the gradual union of small collections of this kind at length destroys the whole muscle. When the suppuration runs a chronic course, the cellular sheath and outer layer of the muscle very commonly change into a thick lardaceo-fibrous membrane: in fact the muscle is converted into a thick-walled bag of matter. Certain muscles are particularly liable to be destroyed in this manner, such as the psoas, and the iliacus; and the disease is well known in the instance of the former muscle by the name of psoas abscess. The sac of the psoas abscess is spindle-shaped or cylindrical, and it is lined sometimes by a soft, diffluent, shreddy tissue, which is soaked in pus or sanies, sometimes by a smooth, grayish-red, or grayish lamina, resembling jelly; it may be full and tense, or collapsed, according to circumstances. At the insertions of the muscle into the bodies of the vertebrae, the sac not unfrequently spreads out into sinuses or pouches, while near the tendon it contracts like a funnel. Rounded bands of softened, or of lardaceo-fibrous and degenerated muscular substance, pass like bridges across the cavity; they take various directions, but are, for the most part, longitudinal. The crural vessels and nerves pass over the sac externally, and are stretched by, and adherent to it. The crural vein is not unfrequently found inflamed, and stopped by a plug of blood. In the further progress of the abscess, the centre of the tendon suppurates, and the sac, thus enlarged, appears below Poupart's ligament, and extends at last quite to the insertion of the tendon.

If the patient does not die from exhaustion at an earlier period, ulceration takes place in the wall of the abscess and the adjoining parts; the matter gravitates in different directions, and is occasionally discharged externally. Caries of the ilium may ensue; the matter may pass under the fascia and among the muscles of the thigh, or towards the great sacro-sciatic foramen; and the abscess may open at the inner side of the thigh, in the abdomen above the groin, in the nates, etc.

In favorable cases the abscess heals up: the matter having been discharged or absorbed, the sac contracts and shrinks to a fibroid (ligamentous) cord, which sometimes retains in its interior chalky remains of inspissated purulent matter.

There is a very frequent combination with this abscess of muscle, and one of considerable importance, the relation of which to the suppuration in the muscle still requires explanation; I allude to caries of the bone into which the upper end of the muscle is inserted. Caries of the ilium, in cases of psoas abscess, is unquestionably consecutive; not so, however, caries of the lumbar vertebrae. This combination of disease in muscle and in bone, is certainly most frequently observed in the instance of the psoas muscle and the lumbar vertebrae; but it is sometimes found existing between the spine, and the tendinous crura of the diaphragm or the long muscles of the neck. I have met with it in other parts also, where muscles are inserted into spongy bones; for instance, at the insertion of the sartorius and gracilis, I have found the bone inflamed, and suppuration commencing in the interior of the tendon. The process is very rarely seen at its commencement; but from an analysis of the combination, as it has occurred to different observers, it seems that in some cases the inflammation and suppuration of the muscle is the primary disease, and the caries consecutive; whilst in others, the bone is first affected, and the abscess is formed chiefly by the subsequent collection and gravitation of the purulent matter.

From what I have had an opportunity of observing, it appears to me extremely probable, that in many cases the bone is the first diseased, whilst in many others the affection commences simultaneously in both structures; in the latter case it usually happens, that the suppuration in the tendon of the muscle spreads, especially at first, with most rapidity.

a. The caries, thus combined with abscess, is almost always of tuberculous nature; as, therefore, tubercle is a very common disease in bone, but is very rare in muscle, it is so far likely that the bone would be first diseased and the muscle afterwards.

b. But, on the other hand, I have met with cases which support the view, that the affection begins simultaneously in the bone and muscle, - cases in which at the insertion of the sartorius, the gracilis, or the long muscles of the neck, the bone was inflamed, and suppuration was commencing in it, whilst the tendon of the muscle formed a funnel-shaped abscess around the diseased spot of bone. Moreover it may be presumed, that this is the way in which the inflammation would extend to the muscle, when the bone is primarily affected.

When the disease has commenced in the manner last described, it extends into, and produces caries in the bone; while on the other side, advancing from the point of the funnel-shaped cavity, it excavates the belly of the muscle: as it spreads it leads to the deposition of a tuberculous exudation, and reduces the muscle to a mere abscess, which communicates through the narrow sinus in the tendon with the ulcerating cavities within the bone.

The contents of the abscess are tubercular, purulent matter, and fragments of necrosed bone, infiltrated with tubercle.

3. Metastasis In Muscles

Deposits of purulent and sanious matter are sometimes found scattered extensively throughout the muscular system; they occur for the most part when pus or sanies has been taken into the mass of the blood.

4. Gangrene Of Muscles

Sometimes inflammation terminates in gangrene; the muscular substance becomes much discolored, and changes into a shreddy, almost diffluent mass, soaked through with sanies, and of a greenish-brown color.

The state of the muscular substance is peculiar beneath an eschar, and in cases of mummification. It is converted either into a dirty reddish, soft, humid, spongy, pap-like pulp, or into a more dry, tinder-like and fragile mass, that shrinks and crumbles together.