Passive Congestion.

Passive Congestion.

Passive congestion is caused by interference with the return of the current of blood from a part.

Old age and debility weaken the tissues and the force of the circulation, especially in the veins, and retard the movement of the blood. We then see horses of this class with stocked legs, swelling of the sheath of the penis or of the milk glands, and of the under surface of the belly. We find them also with effusions of the liquid parts of the blood into the lymph spaces of the posterior extremities and organs of the pelvic cavity.