The hypodermic method consists in injecting medicines by means of a graduated syringe with a sharp-pointed nozzle, and constructed for the purpose, into a subcutaneous cellular tissue, thus producing both a local and general effect, and an impression is made much more rapidly than when the medicine is taken into the stomach. It is necessary that the remedy should be applied beneath the skin, or mucous membrane, and that it should not be injected into any large vessel; hence for hypodermic injections a locality should be selected free from nerves, veins, or large vessels, and not the same locality in subsequent injections. The medicinal agents used for hypodermic injections are now prepared in the form of tablets which are perfectly soluble, and of considerable strength in small bulk. They are dissolved in pure or distilled water at the time the injection is to be made, and great accuracy is thus obtained. Anodynes thus used are more rapid in their effect, and the general rule as regards the quantity is, that in first injections the dose should be, for males, two-thirds of the ordinary dose by the stomach and for females about one-half. It is very necessary that a vein or large vessel should not be punctured when introducing the point of the syringe. The insertion of the deltoid muscle in the arm is generally selected as the place of injection, and the needlepoint of the syringe should not be inserted too deep nor at the same point in subsequent injections. Hypodermic injections may also be made in the back, front of thigh - just in front of trochanters, and in the calf of the leg. A graduated syringe is required, and the point of the needle pushed through the skin, or mucous membrane until it works easily in the tissues beneath ; then inject slowly, and when withdrawing the point, press the finger firmly over the puncture for a minute, to prevent the fluid escaping. The effects of a medicine are much more rapidly obtained by the hypodermic method than when administered by the mouth. In dental practice this method is employed for the relief of neuralgia, and the pain attending the extraction of teeth; also for the administration of ergot in cases of alveolar hemorrhage. There are two dangers from hypodermic injection - the needle may enter a vein and the entire dose may be carried at once to the vital centres, - the solution or needle used may not be sterile and an abscess be produced.

Counter-Irritants

Medicinal substances of the classes of rubefacients and epispastics are employed as counter-irritants, their effect being to establish external or artificial irritation for the relief or cure of internal inflammation existing in a part or in the body. The extent and character of the counter-irritation thus 3 established should be, in a great measure, regulated by the character of the disease which it is intended to relieve; a rubefacient being indicated in irritation of mucous membrane, a seton or issue when the disease is of a suppurative character, and a vesicant in inflammation of serous membranes.

Setons and Issues are employed to produce permanent counter-irritant effects. A seton consists of a skein of silk or a piece of tape or other substance passed through the integument by means of a seton-needle, and allowed to remain, so that a discharge is maintained. A simple seton in the case of an incision into an alveolar abscess, is composed of a single or a double strand of floss silk introduced into the wound made by the lancet, or into the orifice of a fistulous opening, after the pus of the abscess has been evacuated, to maintain a free exit for the pus which may be secreted after the first operation ; fine silver wire is also employed for the same purpose. An issue is generally some irritating substance, such as caustic potassa, or a small pea, or piece of orris root introduced in order to maintain a discharge.

Blood-letting is performed for the purpose of lessening vascular excitement, reducing inflammatory action, relieving congestive pain and spasm, promoting absorption, relaxing the muscles and arresting hemorrhage. It is divided into general and local, general blood-letting consisting of venesection or phlebotomy, the median cephalic or basilic veins of the arm, and occasionally the external jugular and other veins, being the ones selected from which to draw the blood. But it should be resorted to with caution, as it is a powerful and exhausting agent.

Local Blood-letting is chiefly employed for the relief of local inflammations and congestions, and is accomplished by means of leeches, cups, and scarifications.

The leech - hirudo - is commonly employed as an agent for local blood-letting, and is preferable to "cupping" in many local and chronic forms of inflammation; also in infantile affections which require such an operation, when the American leech is used, and it makes a smaller incision than the European leech, and draws less blood. A leech is supposed to draw on an average, about a drachm and a half to two drachms of blood before it is removed, and the quantity which subsequently flows will generally equal that drawn by the leech.

Leeches are often applied to the gum over the root of a tooth affected with acute periodontitis, to relieve the inflammation and congestion. To make the leech bite readily, the surface to which it is to be applied may be smeared with cream or sweet milk, or a puncture may be made in it, so as to draw blood, and, to isolate the part of the surface on which it is desired to apply the leech, a small hole may be made in a piece of bibulous paper, which will adhere to a dry surface of the gum, and afford an opening for the mouth of the leech to approach the surface.

To remove a leech if it does not drop off" of its own accord which they will generally do in from fifteen to twenty minutes, it may be sprinkled with a little cold water or diluted vinegar, or powdered sugar. To promote bleeding from leech bites, fomentations or warm dry cloths, or a cupping glass, may be used. To check the hemorrhage from leech bites, which is sometimes excessive, firm pressure may be made with the finger, or exposure to cold air, or the application of such styptics as alum or matico.

Cupping is employed when it is desired to draw blood rapidly, or to ascertain the exact quantity of blood drawn, or when it is desirable to make an impression on the system. Cupping is performed by means of cupping glasses and a scarificator. The glasses are applied after being partially exhausted of air, when the removal of the atmospheric pressure produces a determination of blood to the capillaries of the part, and it is afterwards easily drawn by scarification.

Scarifications consist of small incisions made in inflamed and congested parts, to relieve the engorged condition of the capillary vessels, and are sometimes employed to relieve acute inflammation of the gums and mucous membrane of the mouth.