Atrophy (Gr. hunger, from a privative and nourishment), in medicine, the wasting away of any organ or portion of the body from want of nutrition in the part, irrespective of the general nutrition of the body. The principle of vitality decreases in the organ when its functions are suspended, and nutrition slackens where the vital principle becomes inert. The mammary glands or milk-secreting organs, in the breasts of women who have passed the age of child-bearing, are sometimes so much atrophied that traces of them only can be found imbedded in large lobes of adipose tissue or fat. In contrast with atrophy is hypertrophy, or excessive nutrition and enlargement of an organ or set of organs in the body. Any limb or portion of a limb artificially compressed for a long time will be depressed in its vitality, and lack the power to appropriate nutrition from the blood; it will gradually diminish in size and force, and become atrophied. Disuse alone, without compression, will cause atrophy in the upper or the lower limbs, or even in the whole body; for many persons waste away from morbid inactivity, which brings on by degrees emaciation and debility, resulting in decay of the whole system. - Paralysis, by preventing natural exercise in the limbs, may depress the vitality of the parts, and diminish their powers of nutrition.
This will cause atrophy, or a falling away of the paralyzed limb. The dislocation of a joint, if neglected, may, by causing pressure on the nerves, cut off a portion of the innervation necessary to maintain the active functions of nutrition in the parts below, and thus depress vitality and bring on atrophy. In children of a scrofulous diathesis, disease in the hip joint often affects the nerves of the parts and the vitality of the whole limb, diminishing the powers of nutrition, and causing the leg to dwindle in comparison with the one which is not affected. In these cases the atrophy is of a double nature; for the gluteal muscles waste away, and the bones decay in part, before the limb begins to dwindle in its general proportions from the weakened powers of nutrition.