The _hydrochlorate_ (muriate of ammonia—sal-ammoniac)—is known by its solid, white, crystalline appearance; its ductility; its volatility; and by the effect of caustic potass and nitrate of silver, the former of which disengages an ammoniacal odour, while the latter causes in a solution of the salt a white precipitate, the chloride of silver. _Of the action of the Ammoniacal Salts, and their effects on man._—To determine the action of ammonia on the animal system, Professor Orfila injected sixty grains of the pure solution into the jugular vein of a dog. Immediately the whole legs were spasmodically extended; at times convulsions occurred; and in ten minutes it died. The chest being laid open instantly, coagulated florid blood was seen in the left ventricle, and black fluid blood in the right ventricle of the heart. No unusual appearance was discernible any where else except complete exhaustion of muscular irritability.[468] The experiments of Mr. Blake also show that ammonia introduced in large doses into the veins acts by suddenly extinguishing the irritability of the heart. Small doses first lower arterial pressure from debility of the heart’s action, and then increase it by obstructing the systemic capillaries. When injected into the aorta from the axillary artery, it causes great increase of arterial pressure, owing to the latter cause; and then arrests the heart, while the respiration goes on. Four seconds are sufficient for the ammonia to pass from the jugular vein into the heart, so as to be discovered there by muriatic acid causing white fumes.[469] Half a drachm of a strong solution, introduced by Orfila into the stomach of a dog and secured by a ligature on the gullet, caused at first much agitation. But in five minutes the animal became still and soporose; after five hours it continued able to walk; in twenty hours it was found quite comatose; and death ensued in four hours more. The only morbid appearance was slight mottled redness of the villous coat of the stomach. A third dog, to which two drachms and a half of the common carbonate were given in fine powder, died in twelve minutes. First it vomited; next it became slightly convulsed; and the convulsions gradually increased in strength and frequency till the whole body was agitated by dreadful spasms; then the limbs became rigid, the body and head were bent backwards, and in this state it expired, apparently suffocated in a fit of tetanus.[470]