Thus a poison may be defined as a substance \\inch, when taken into the body, is capable of influencing the molecular characters of the organ or organs so that the function of the organ or organs involved is materially altered from the normal. Such alterations from the normal may go on to death, or they may go on simply to toxic action and recovery. This, as has already been stated, depends largely on the individual, on the organ acted upon, and on the close. Problems of absorption and resorption and of elimination are all subjects of investigation by the toxicologist, and do not involve the layman.
Poisons have been classified, from the more general point of view, purely according to the kind of changes that they bring about in the living proto plasm ; and some toxicologists have defined all poisons as being (r) oxidising poisons, such as oxygen, hydrogen peroxide, phosphorus, arsenic. perman ganate of. potassium, etc. ; (2) catalytic poisons, such as the anesthetics, ether, chloroform, alcohol, etc. ; (3) a group which acts by forming salts with the protoplasm of the body-cells, such as the mineral acids, solutions with mineral bases, and salts of the heavy minerals ; and (4) a group known as substitution poisons, in which some chemical radical of the poison enters into combination with and replaces some chemical radical of the tissue. The most important of these are carbolic acid, sulphur dioxide, the various alkaloids. etc. Such a classification, while appealing to the chemist and to the student of the philosophy of pharmacology, has little application in a general work. Most modern writers, therefore, divide all poisonings into acute and chronic forms. Under acute poisons the principal group consists of those that act locally. They are the cause of local irritations, which may go on to destruction of tissue. Such are the acids : sulphuric, hydrochloric, hydrofluoric, nitric, chromic, formic, oxalic, lactic, etc. ; the strong alkalies, such as soda, potash, ammonia, calcium, etc. ; special irrita ting resins, such as are found in cantharides, and in the oils of turpentine, cubebs, juniper, mezereon, pennyroyal. poison-ivy, etc. All these substances act directly at the point of application. The acids and alkalies have the property of combining with the water in the tissues, abstracting it, and causing changes in the protoplasm, some liquefying it (as potash and soda), others charring and drying it (as sulphuric acid, nitric acid, etc.). The skin or mucous membrane acted on by these poisons, depending on the concen tration of the substance and the length of time of the action, is first reddened, then there is an exudation of serum in the tissue, burning and destruc tion takes place. ulcers are formed, and the skin or mucous membrane is
entirely destroyed. Pain is produced by the action, which is usually very acute in character ; and when the substances are taken into the stomach they usually cause nausea, vomiting (which may be bloody), excessive saliva tion, mucus slime, intense pain in the entire abdomen, with a feeling of collapse, weak, rapid pulse, cold extremities, blue lips, and, if the patient lives long enough, cholera-like diarrhoea. Convulsions and coma usually precede death. The irritating resins do not, as a rule, act so intensely ; vet the symptoms are much the same. Destruction of the tissue is not so marked, and in case of the volatile oils one gets the symptoms of this class of drugs.
The treatment of acute poisoning by acids consists in the free adminis tration of mild alkalies. Thus, lime-water in copious doses is one of the best remedies. It is usually combined with milk or with albumen, being beaten up with white of eggs, so that one gets the action of the alkaline antidote and the demulcent action of the albumen as well. Mucilages, such as gum arabic and gum tragacanth, are also useful in the treatment of poisoning by acid. If lime-water is not available, one can scrape plaster from a wall, and, after straining, use the water in which it has been left for a short time. The treatment of burns on the surface of the body, following the action of caustic acids, is similar to the general treatment of burns, antiseptic salves, such as oxide-of-zinc ointment, being the most ‘videly used remedies.
Poisoning by alkalies is best treated by weak acids. Here the most efficacious acids are vinegar, and lemon or lime juice, either pure or as weak solutions of citric acid. In either case a prompt washing-out of the stomach with water which has been made alkaline in the case of acid-poison ing, and acid in the case of alkali-poisoning, is important. The special diagnosis of the specific acid or alkali which has caused the poisoning is a technical problem which, as a rule, only the physician is capable of solving. There are no special modes of treatment for poisoning by the volatile oils and the resins just enumerated. The after-treatment usually consists of rest and demulcents, such as white of egg, mucilage, starch-paste, etc.