5. Senile hypertrophy is connected with nutritional disturbances characteristic of old age, as to whose remote causes we are still uncertain. Instances of senile hypertrophy, however, are common, particularly in the prostates of elderly men, which are liable to undergo extensive enlargement.
6. Of congenital hypertrophy and that of unknown origin we see, for instance, examples in certain rare cases of hypertrophy of the breast, in leontiasis, perhaps even in acromegaly, etc.; and these are to be distinguished from gigantism, because in most instances of the former type the hypertrophic tendency is not manifested until youth or adult life, whereas gigantism is a condition in which the tendency was apparent even before the birth of the individual.
ATROPHY.
Atrophy implies impaired nutrition, and means diminution in the size of an organ or part, and is the converse of hypertrophy. It is necessary to make plain that in atrophy nutrition is only impaired and not arrested, since complete arrest of nutrition means necrosis—i. e., gangrene or disappearance of parts. It may be—
| A. | Physiological | - | 1. | From disuse without disease; | |
| 2. | Biological or developmental; | ||||
| 3. | Senile. | ||||
| B. | Pathological | - | 4. | Result of acute tissue losses; | |
| 5. | Result of phagocytic activity; | ||||
| 6. | Result of continuous pressure; | ||||
| 7. | Specific. | ||||
A. Physiological Atrophy.
—1. This is always the result of disuse or impaired function from any cause. Its evidences are generally seen in the fatty structures and muscles—i. e., in the soft parts. It is true, however, even of the bones, or, of greater interest, even in the brain cells. We see evidences of it also in minute organs; as, for example, in the digestive glands in certain cases where diet is restricted. Again, we see it in the diminution of the size of the heart after hip amputation, less being required of that organ, and also in the entire structure of the rectum after colostomy.
2. Examples of the developmental type are best seen in the natural disappearance of the hypogastric arteries, the ductus arteriosus, the vitelline duct, the Wolffian bodies, and in the various generative ducts (Gärtner’s, etc.) shortly after the birth of the human individual. We sometimes see it also in the prostate after orchidectomy. Equally illustrative is the disappearance of the tail and gills of the tadpole, the eyes of animals living in caverns, and, in a general way, of organs which become useless owing to a different environment.
3. Senile atrophy is seen equally well in the hair follicles, the teeth, the bones, and the sexual organs of elderly people—in fact, in all their tissues, even in the brain.