• Tn heart failure and arterial and pulmonary hypertension, the preservation of normal hemodynamics, of clinical compensation, and eventually of the patient's life, depends to a great extent on a stable, compensatory hyperfunction of the heart. When the hyperfunction of most organs takes place in a healthy individual as a reaction to physiological stress, ordinarily it is transient and disappears after the cessation of the stress. On the other hand, compensatory hyperfunction of the heart, caused by destruction of the valves or bv persistently high arterial blood pressure, is protracted, for the lesions that have developed in the body are irreversible and the continuity of hyperfunction becomes necessary tc\life. Folborth, 1 while\studying the relationship between exhaustion and restoration in organs subjected to high functional strain, came to the conclusion that: repetition of functional stresses may cause two opposite states to develop. When the organ has had time to attain a state of/complete restoration after a preceding exhaustion, it becomes adapted and its working capacity is gradually enhanced. When it is subjected to sustained activity before having attained a condition of stable restoration, it becomes chronically exhausted.