Circulatory Disturbances

Anemia may be part of a general condition or the result of local interference. Degenerations of the muscle occur if the anemia has been sufficiently severe or long continued.

Hyperemia occurs during exercise and in inflammatory processes.

Hemorrhage results from injuries or from the rupture of a blood-vessel that is either diseased or in which the blood-pressure has been too great.

Degenerations

Necrosis of muscle-fibers may follow injuries, burns, and various local causes; the tissue becoming blackish in color and disappearing.

Cloudy swelling is found in infectious and toxic conditions in general and in the neighborhood of inflammatory changes and tumors. The sarcoplasm becomes very granular and the striations disappear. Fatty degeneration frequently follows.

Fatty metamorphosis follows the cloudy swelling when the original cause has been very harmful, as in phosphorous and arsenic poisoning. The muscles are flabby and yellowish in color. The fibers lose their striations and become filled with fat-drops.

Fatty infiltration consists of the deposit of fat between the muscle-fibers. It is most typical in pseudohypertrophic muscular atrophy, but may be present to some extent in obesity.

Amyloid degeneration is rare in voluntary muscles, but occurs occasionally in the non-striated.

Calcification occurs in the form of ossifying myositis.

Hyaline Degeneration

In this the muscle-fibers become granular and cloudy, and the transverse striations are obscured. The hyaline change appears in streaks, the fibers having become transformed into a homogeneous mass within the sarcolemma. The fibers break in two, and rupture of the muscle may occur. The degeneration is found in the course of infectious conditions, as typhoid fever and smallpox. It is found usually in the rectus abdominis, in the long muscles of the thigh, in the diaphragm, and in the heart.

Atrophy

Simple atrophy is usually either senile or the result of inaction. The fibers become smaller, and there is usually some hyperplasia of the connective tissue. Brown atrophy is quite common as a senile change. In it brown pigment particles are deposited in the muscle-fibers near the nuclei, and impart a brown color to the tissue.

Progressive muscular atrophy usually involves the muscles of the hands, arms, and shoulders, but may attack those of the diaphragm and back. The muscles are pale and flabby, and show various degenerations, such as transverse division, longitudinal separation, coagulation necrosis, and vacuolation. At the same time there is a connective-tissue hyperplasia.

Pseudohypertrophic muscular atrophy commonly makes its appearance in the muscles of the calf, thigh, and upper extremities. The muscles are much larger than normal, but are soft and flabby. Microscopically there is seen a great hypertrophy of the intermuscular connective tissue, with fatty infiltration and atrophy of the fibers.

Many of the muscular atrophies depend upon various obscure nerve lesions, as such changes are found in syringomyelia; acute anterior poliomyelitis; lateral scleroses; in degeneration of the peripheral nerves; in diseases of the anterior nerve-roots; in diseases of the pons, and possibly of the nerve-endings.

Inflammation or myositis is generally the result of inflammatory changes in adjacent tissues. It may be acute or chronic, local or disseminated.

The process is usually not severe; the muscle is swollen, reddened, and there is a slight exudation, as well as a round-cell infiltration. Some of the fibers may degenerate.

Hemorrhagic myositis is characterized by marked hemorrhagic infiltration into the muscle. It may follow extension from gangrenous processes near by.

Purulent myositis is characterized by local or disseminated abscess formations, with necroses and breaking-down of the muscle-fibers. It is due to infection by micro-organisms as a result of traumatism through conveyance by the blood or lymphatics or to infectious emboli. In the healing, masses of connective tissue may form and occasion more or less severe deformities, due to shortening. Sometimes an abscess may become encapsulated and calcified.

Acute disseminated polymyositis is a condition in which many muscles are simultaneously affected. It is of infectious origin. There is round-cell infiltration between the fibers, many of which show degenerative changes.

Chronic myositis may be a slow process, found in tuberculosis and actinomycosis, in which there is long-continued suppuration without fibrosis. The ordinary form is the myositis fibrosa, in which there is a slow increase in the amount of connective tissue with degeneration and atrophy of the muscle-fibers. It follows acute myositis and sometimes after certain nerve-lesions.

Myositis ossificans is a chronic inflammatory condition in which there is actual bone-formation within the intermuscular connective tissue, in fascia, and tendons. It is found in the deltoid, pectoral, and adductor muscles, and appears to be the result of long-continued and repeated slight injuries.

Myositis ossificans progressiva is a peculiar condition beginning in the muscles of the back of the neck. The ossifying process gradually extends to other muscles of the trunk. The deposit of bone may become very great and cause marked interference with muscular contraction.

Tuberculosis of the muscle is commonly secondary to lesions in adjacent tissue, and appears either in the form of caseous degeneration, cold abscess, or of fibrous formation. Hematogenic infection is uncommon in general miliary tuberculosis, but may occur.

Syphilis is rare, but may be found in the form of gummata, or as a diffuse hyperplasia of the muscular septa, with atrophy of the muscle-fibers. The muscles usually involved are the biceps, masseter, tongue, and back.

Glanders and actinomycosis may involve the muscles by extension.

Tumors, as a rule, originate within the intermuscular connective tissue and may be any one of that type - lipoma, fibroma, etc. The sarcoma is not infrequent in any of its combinations, and may be spindle- or round-celled in type. Carcinoma is always secondary, and is found in the neighborhood of similar growths in the mammae, stomach, skin, etc., as a diffuse infiltration.

Parasites are not uncommon, the most frequent being the Trichina spiralis, the Cysticercus cellulosoe, and the Taenia echinococcus.