PARTS TO WHICH MEDICINES ARE APPLIED. 47 with a small, sharp lancet, and, for the better regulation of the dose, it is desirable that the syringe should be graduated. It is important to avoid the puncture of a vein, lest a suddenly overwhelming effect be produced; and, with this view, the syringe-needle should not be pushed too deeply into the tissues, and should be withdrawn a little, to allow a wound of a vein to close from elasticity. When a constitutional effect only is aimed at, non-sensitive, vascular parts should be selected, in order to facilitate absorption and give little pain, such as the waist; another good spot for injection is at the insertion of the deltoid muscle in the arm, and, where repeated operations are practiced, it is well to vary the point of injection. Irritating injections are best tolerated in the back. To preserve hypodermic solutions from the destructive action of a low order of vegetation (alga), cherry laurel water or a weak borax solution may be used. 2. To Mucous Membranes.-Medicines are applied to all the gastro-pulmonary and genito-urinary mucous surfaces. a. To the conjunctiva they are applied for local effects only, and are termed collyria, or eye-washes. b. To the nasal or pituitary membrane, they are applied usually for local purposes; sometimes, however, to irritate and excite a discharge, when they are termed errhines; sometimes, also, to produce sneezing, with a view to the expulsion of foreign bodies from the nasal cavities, when they are termed sternutatories. c. To the mucous membrane of the mouth and throat, medicines are applied almost exclusively for local purposes. When in solution, they are termed gargarismata or gargles. Powders are introduced by insufflation. d. To the Eustachian tubes, washes are applied in local affections. e. On the aërial or tracheo-bronchial membrane, medicines produce a very decided influence, both local and general. Liquid substances are introduced into the air-passages by means of a sponge or syringe, in the treatment of chronic inflammations of the larynx. Various substances are inhaled with advantage in phthisis, chronic bronchitis and laryngitis, asthma, etc., while A variety of circumstances, relating to the human organism, modify the effects of medicines. Age exerts a most important influence in this particular. Children are more susceptible than adults; and in advanced age, also, smaller doses are required than in the prime of life. No general rule can be laid down for the adaptation of the doses of medicine to different ages, as the susceptibilities to the influence of different medicines are unequal at the same age. Thus, infants are peculiarly alive to impressions from opium, while in the cases of calomel and castor oil, they will bear much larger proportional doses. Dr. Young's scheme for graduating the doses of medicines to different ages answers very well in prescribing: For children under twelve years, the doses of most medicines must be diminished in the proportion of the age to the age increased by 12; thus, at two years to 4, viz.:. At 21 the full dose may be given. 2+12 A good practical rule for graduating doses is that of Dr. Cowling: "The proportional dose for any age under adult life is represented by the number of the following birthday divided by twenty-four:" for one year 24; for three years, ; for eleven years, 1 = 1. = Sex, temperament, and idiosyncrasy, all modify the effects of medicines. Women require somewhat smaller doses than men ; and during menstruation, pregnancy, and lactation, all active treatment, which is not imperatively demanded, should be avoided. To persons of a sanguine temperament, stimulants are to be administered with caution, while, in cases of the nervous temperament, the same care is to be observed in the employment of evacuants. Mercurials are called for where the bilious temperament exists, but, on the other hand, they are generally injurious where the lymphatic temperament is strongly marked. Idiosyncrasy renders many individuals peculiarly susceptible or insusceptible of the action of particular medicines, as mercury, opium, etc. In disease, an extraordinary tolerance of the action of many medicines is established. In tetanus, immense quantities of opium are borne and required; in typhoid fever, alcohol is PARTS TO WHICH MEDICINES ARE APPLIED. 45 freely administered without inducing narcotism; in pneumonia, tartar emetic may be taken in large doses without nausea. The time of administration modifies the action of medicines. Where a rapid effect is desired, they are to be given on an empty stomach; on the other hand, irritant substances, as the arsenical or iodic preparations, are best borne when the stomach is full; and the insoluble chalybeates, requiring the gastric fluid to dissolve them, should be taken with the food. The condition of the stomach is to be considered in prescribing medicines. In the black vomit of yellow fever absorption cannot take place by the stomach, and in the second stage of cholera, endosmosis by the bowels is impossible; here, the hypodermic medication is invaluable. Habit diminishes the influence of many medicines, especially narcotics. The influence of race, climate, occupation, and the imagination, upon the effects of medicines is often decided, and deserves attention in prescribing. PARTS TO WHICH MEDICINES ARE APPLIED. Medicines are applied to the skin, to mucous membranes, to serous membranes, to wounds, ulcers, cysts, and abscesses, and they are injected into the veins. 1. To the Skin-Medicines are applied to the skin for both a local and a general effect; when brought in contact with the skin without friction it is termed the enepidermic method. As their influence on distant organs is the result of their absorption, this function must be taken into consideration. Solutions of medicinal substances in water permeate slowly through the skin to enter the vessels. M. Hebert first drew attention to the fact that the oily secretion of the sebaceous follicles of the skin prevented the contact of aqueous liquids with the cuticle, but the cuticle itself is the main impediment to absorption. Waller (The Practitioner, London, 1869, vol. iii, p. 330) found that chloroformic solutions of the alkaloids placed in contact with the skin readily produced their effects upon the system. He ascertained that chloroform quickly osmoses through the skin, carrying with it dissolved substances, and that the rationale of the process was not due to a solvent action on sebaceous matter. The application of medicines to the skin by friction, the epidermic method, is occasionally resorted to, but its results are slow and uncertain; and when we wish to affect the system through the agency of the skin, the preferable method is to apply the medicine to the dermis denuded of the cuticle. This is termed the endermic method, and the cuticle is usually removed by means of a blister. The medicine is applied to the denuded dermis in the form of powder, or, if very irritating, it may be incorporated with gelatin, lard, or cerate. This method is useful in cases of irritability of the stomach, of inability to swallow, or where we desire to influence the system rapidly and by every possible avenue, or where it is of importance to apply the medicine near the seat of the disease. The dose is to be two or three times the amount which is administered by the stomach. Another method of applying medicines through the skin is by injection into the subcutaneous cellular tissue. This method is termed the hypodermic method, and is of recent introduction into therapeutics. Medicines are injected hypodermically for both a local and a general effect. A constitutional impression can be produced by this means more certainly, rapidly, and efficiently than by the introduction of medicines into the stomach. It is particularly adapted to the speedy relief of pain, to the treatment of diseases in which it is desirable to influence the system with the greatest possible rapidity and effect, and also to cases where the internal administration of medicines is interfered with. The substances proper for hypodermic injection are those which are small in bulk and are of perfect solubility, such as the vegetable alkaloids. Substances of imperfect solubility should not be injected hypodermically, dangerous results having followed therefrom, as from the use of the salts of quinine. The dose, particularly in first injections, should be two-thirds of the ordinary dose by the stomach, and for females about one-half. The instrument used for injection is a small syringe armed PARTS TO WHICH MEDICINES ARE APPLIED. 47 with a small, sharp lancet, and, for the better regulation of the dose, it is desirable that the syringe should be graduated. It is important to avoid the puncture of a vein, lest a suddenly overwhelming effect be produced; and, with this view, the syringe-needle should not be pushed too deeply into the tissues, and should be withdrawn a little, to allow a wound of a vein to close from elasticity. When a constitutional effect only is aimed at, non-sensitive, vascular parts should be selected, in order to facilitate absorption and give little pain, such as the waist; another good spot for injection is at the insertion of the deltoid muscle in the arm, and, where repeated operations are practiced, it is well to vary the point of injection. Irritating injections are best tolerated in the back. To preserve hypodermic solutions from the destructive action of a low order of vegetation (algæ), cherry laurel water or a weak borax solution may be used. 2. To Mucous Membranes.—Medicines are applied to all the gastro-pulmonary and genito-urinary mucous surfaces. a. To the conjunctiva they are applied for local effects only, and are termed collyria, or eye-washes. b. To the nasal or pituitary membrane, they are applied usually for local purposes; sometimes, however, to irritate and excite a discharge, when they are termed errhines; sometimes, also, to produce sneezing, with a view to the expulsion of foreign bodies from the nasal cavities, when they are termed sternutatories. c. To the mucous membrane of the mouth and throat, medicines are applied almost exclusively for local purposes. When in solution, they are termed gargarismata or gargles. Powders are introduced by insufflation. d. To the Eustachian tubes, washes are applied in local affections. e. On the aërial or tracheo-bronchial membrane, medicines produce a very decided influence, both local and general. Liquid substances are introduced into the air-passages by means of a sponge or syringe, in the treatment of chronic inflammations of the larynx. Various substances are inhaled with advantage in phthisis, chronic bronchitis and laryngitis, asthma, etc., while |