"Nitro-glycerine was discovered by Sobrero in 1847, but none could be obtained for physiological experiment until Morris Davis, a Philadelphia chemist, in the same year, after long and laborious trials, under direction of Hering, succeeded in producing the substance in sufficient quantities for proving." I quote this from the Guiding Symptoms. Glon. is one of the many monuments of Hering's therapeutic genius. It is to him that we owe the introduction of this notable remedy into the materia medica, and into medicine. The note of the action of Glon. is a tendency to sudden and violent irregularities of the circulation. It acts very quickly and very violently. The "signature" of this potent explosive may be said to be "bursting" and "expansion." Bursting, throbbing headaches; sensations of expanding in the head and elsewhere. Throbbing of carotids; violent action of heart; rush of blood to head; flushes of heat rising from chest to head, then throbbing pain in head. The characteristic neuralgias of Glon. are accompanied with much throbbing, and are often < at night, preventing sleep. Supra-orbital neuralgia, pulsating; retinal congestion from exposure to strong light. Facial neuralgia, extending through head. Cardiac neuralgia (angina pectoris) with radiating pains. Guernsey, with his usual graphic terseness, says that Glon. is suited to "Troubles of the head in type-setters, and in men who work under a gas-light steadily, so that the heat falls on the head; bad results from sunstroke; can't bear any heat about the head; can't walk in the sun, must walk in the shade or carry an umbrella; can't bear heat from a stove; great vertigo on assuming an upright posture, from rising up in bed, rising from a seat, &c. Heat in the head; throbbing headache." The great sensitiveness to the least jar, which is a very marked feature of the Glon. headache, causes the patient to carry his head very carefully in order to avoid the chance of it. The headache is in the whole head and every part—forehead, vertex, occiput. Many pains appear in occiput and base of brain; gnawing in occiput; sore pain; pressure; severe pain in occiput, extending to eyes and temples; sensation as if something were moving in nerves from back of neck upward to head. The eyes may be fixed or protrude; aversion to bright light; black spots before sight. Face flushed or pale. Climacteric disturbances. Fainting, sudden unconsciousness; convulsions, especially during labour. Nausea and vomiting of cerebral origin. Violent, stabbing, neuralgic pains, so violent as to make patient frantic, he wants to escape, to jump out of window. Bad effects of fear; horrible apprehension; fear of being poisoned. A characteristic mental condition is loss of sense of location: "well-known streets seem strange to him." Among the peculiar sensations are: Chin feels too long. Chest feels screwed together. Brain as if expanding; as if moving in waves; as if hanging with head downwards; as if something were pumped into vertex; as if everything were crowded out at forehead; as if warm water were running upwards from nape of neck; as if the neck were gripped by a hand; as if some one were pulling eyes from within outward. Noise in left ear as if it came from heart. Lower lip feels swollen. As if heart would rise to throat. Pains are: Bursting; throbbing; pulsative; tearing; piercing; stabbing; gnawing. Burning between shoulders. Sitting or lying still, or walking in cold air > headache. Bending forward; bending head backward, and almost every movement < headache. Rest < pain in knee. Excessive heat and cold = hyperaemia of brain. Heat generally <; cold applications and cool air >; but cold water applied to head < head symptoms, even = spasms. < Damp weather. Bad effects of having hair cut; of exposure to sun or fire heat. All summer, headache < every day with the sun. < From wine. Pains from within outward; from front to back. Bad effect of too much riding or driving; sea-sickness; < from jarring. Pressure > headache. Cannot bear weight of hair; clothing seems too tight. Suited to: Florid, plethoric, sensitive women; nervous, sanguine, readily affected persons. Old scars break out again.