INFUSION, in pharmacy, an aqueous so lution of a medicinal substance obtained by -treating with water, usually without the aid of .boiling. The water may be either hot or cold, varying with the object to be obtained. Ac cording to the directions of the United States Pharmacopceia, infusions are generally pre pared by pouring boiling water upon the drug and macerating in a tightly closed vessel until the liquid cools. The active principles are in this manner extracted more rapidly and, as a rule, in much larger portions than if the solution is colder. Heat is not advisable if the active prin ciples are volatile. If an infusion is desired of a greater degree of concentration than that ob tained by the process of maceration, it is fre quently prepared by percolation, in which op eration the drug is sliced or broken up into small fragments, packed in a percolator, and the water, either hot or cold, is passed through. Infusions are sometimes made with the aid of other liquids than water, but this is the excep tion rather than the rule. Infusions do not keep well, and therefore they should be made extemporaneously and in small quantities. In household medicine, infusions are very widely employed. These may be made at home or
made by the pharmacist. It is essential to re member that if they are made in hot weather in large quantities they must be sterilized.
Infusion of saline solution into the blood vessels is a very important procedure in medi cine. It is employed largely in the treatment of shock and in severe hemorrhage, especially following operations or childbirth. The solu tion that is used is known as a normal salt solution and consists of about one teaspoonful of common salt to a pint of water. This solu tion should be boiled carefully for one-half to three-quarters of an hour, the amount of evapo rating water being made up as the boiling pro ceeds, and after being made it should be kept in large bottles provided with cotton plugs for stoppers. In severe cases of hemorrhage, in.; fusion has often saved life, as it provides a body of fluid on which the heart and blood vessels can act. The salt-solution is usually in troduced into one of the large veins of the arm at a temperature of one to two degrees above that of the body temperature. See BLOOD; TRA.NSFUSION.