PROPERTIES.--White or nearly translucent, orthorhombic prisms, octahedral crystals, or a crystalline powder; odorless and having a faintly bitter taste; slightly efflorescent in warm air. Soluble in water, alcohol, ether and chloroform. DOSE.--Dogs, ¹⁄₄ to 1¹⁄₂ gr. HEROIN--DIACETYLMORPHINE This drug is a derivative of morphine, and is now used extensively in human medicine as a substitute for morphine and codeine. PROPERTIES.--White or colorless, crystalline powder, possessing a slightly bitter taste. Insoluble in water, but readily soluble in weak acidous solutions. Heroin hydrochloride is a white, crystalline powder, odorless, soluble in 2 parts of water. Heroin surpasses both morphine and codeine therapeutically in many ways. It increases markedly the inspiratory and expiratory force, while lessening the number of the respiratory movements and exerts a special sedative influence on the respiratory mucous membranes. The drug acts also as a general motor depressant, hypnotic and analgesic, but is not comparable to morphine in these respects. Heroin is about five times more toxic for dogs than morphine. Heroin is particularly valuable in the treatment of all varieties of coughs affecting the dog. The after-effects of small doses are not as nauseating or constipating as morphine. Heroin can be given in powder, pill or tablet, the Heroin hydrochloride in solution, every three or four hours. DOSE OF EITHER.--Horses, ¹⁄₂ to 2 gr.; dogs, ¹⁄₂₄ to ¹⁄₆ gr. ACTIONS.--Opium is analgesic, hypnotic, diaphoretic, antispasmodic, narcotic; also cardiac and respiratory depressant after primary brief stimulation. MEDICAL DOSES.--It dries all secretions except the mammae and skin. The latter being increased, it produces dryness of the mouth and throat, arrests gastric secretions, retards digestion and causes anorexia (loss of appetite); it stimulates the brain by increasing the blood supply; in man it stimulates the mental activity, while in animals it stimulates motor activity; it does not affect the conductivity of nerves, but it prevents the consciousness to pain by paralyzing the nerve centers; the action of the heart is increased and arterial tension is raised; the pupil slightly contracted; the mind at first stimulated, becomes calm, sleep follows, disturbed by dreams and headache; constipation and some depression follows. LARGE DOSES.--Arrest digestion, cause nausea and vomiting, greatly increase perspiration, prevents the conductivity of nerves, depresses the heart and circulation, impairing oxidation and lowering temperature; it contracts the pupil by stimulating the motor nerve of the eye (in horses it dilates the pupil) and causes intense puritis (itching), especially of the nose, often retention of the urine and soon profound sleep; in some cases coma or delirium, leaving as after-effects nausea, depression, constipation, vertigo, anorexia, nasal puritis and fetid pathological secretions.