however, the bulk is too large to be moved by such simple means, and while a messenger is sent for a surgeon to bring the proper instrument, endeavours should be made to keep up a partial supply of air in the lungs, by means of the bellows. POISONS. Those substances which, when taken into the body, or applied externally, always produce such an effect or disturbance in the animal economy, as to induce disease, or a chain of symptoms that if uncorrected would eventuate in serious mischief to the health of the body, or even induce death. Or, to simplify the explanation: a poison is any agent capable of producing a morbid, noxious, or dangerous effect upon anything endowed with life. All poisons are _common_ or _relative_: by the first, is understood those substances which produce morbid or dangerous symptoms on all conditions of animal life, on man as well as on the brute, on the fish as well as the fowl. By _relative_ poisons is understood those agents which are only poisonous to man, or some particular species of animals; thus aloes, which is a useful medicine to man, is poisonous to dogs and wolves; and others which are deadly to the horse, form a nutritious food to the ox. As an instance of the _common_ poisonous agent, affecting all animals in the same manner, may be advanced arsenic and corrosive sublimate. Agents or substances are poisonous only in regard to their dose, the part of the body they are applied to, and the subject on which they are applied. To illustrate these facts, it is sufficient to say that both arsenic and corrosive sublimate are valuable medicines in certain modified doses, while in excess, they are deadly; secondly, a poison to the stomach may be innocuous to the lungs, or what would be fatal to the integrity of the system, applied to one part of the body, is harmless when administered to another; thus the carbonic acid gas which we imbibe with exhilarating satisfaction with our malt-liquor, soda-water, and champagne, is a deadly poison if instead of going down the gullet, it should descend the windpipe, and enter the lungs. There are only _four_ ways by which a poison can enter the system, and prove injurious or fatal to life; of these the most common is by the mouth into the stomach, by the air passages into the lungs, by absorption through the skin, either in its natural state, or from an abrasion or scratch; and lastly by the bowels, from an enema. But whichever way they enter the system, they only re-act upon it in _two_ forms of action; that is, that they are either absorbed into the blood, and conveyed by the circulation to the part or parts affected, or they produce an immediate influence on the nerves of the part with which the poison first comes in contact; and by a sympathetic action affect the whole nervous system. Poisons may belong to either of the three kingdoms, the _animal_, _mineral_, or the _vegetable_, but as the symptoms produced are sometimes nearly the same, from whichever class