The best examples of the _hyperemia of paralysis_ are perhaps to be met with after certain injuries to nerves, as, for instance, flushing of the face and hypersecretion of nasal mucus, tears, etc., after injury to the cervical sympathetic. Such, too, in its essentials is that form of shock known as brain concussion, which is often followed by nutritive disturbances among the brain cells, with consequent perversion of brain function. Waller’s experiment of placing a freezing mixture over the ulnar nerve at the back of the elbow is also significant, the result being congestion and elevation of surface temperature of the fingers supplied by this nerve. Congestion and swelling have also been observed after fracture of the internal condyle of the humerus, by which this nerve was pressed upon; and similar phenomena may be noted in fingers or toes as the result of injuries of other nerves. Hyperemia due to _paralysis of the perivascular ganglia_ is observed sometimes in transplanted flaps, in the suffusion of a limb after removal of the Esmarch bandage, in the congestion of certain sac walls after tapping, in the hyperemia of, perhaps even hemorrhage from, the bladder wall after too quickly relieving its overdistention, and in the swelling of the extremities when they begin to be first used after having been put at rest because of injury. The _hyperemias of dilatation_ are more acute in course and manifestation. Along with them go sharp pain, hypersecretion of glands, edema, and sometimes desquamation of superficial parts. The facial blush due to effusion; the temporary flushing due to indulgence in alcohol; the suffusion of the conjunctiva, perhaps the face, with hyperlacrymation, accompanying facial neuralgia or hemicrania; and the hyperemia consequent upon herpes zoster, urticaria, etc., are illustrative examples of this form. The erythema due to nerve irritation or injury, the swelling of the joints which appears after similar lesions, and that condition described by Mitchell as _erythromelalgia_, probably also belong here. In fact, almost all the reflex hyperemias are hyperemias of dilatation. The forms of hyperemia considered above belong mainly to the designation of _active_.