The term hypodermic is used in conformity with the nomenclature already existing—as "epidermic," " endermic," etc.—but the termination of the word is now altered in deference to the opinions of the best philologists. The term hypodermic, which has been universally adopted, is known to be formed on wrong principles, and hence, in accordance with the rules of construction, the word hypodermatic is substituted. As the term indicates, by this method the medicine is applied to the subcutaneous areolar tissue. This does not include the method of "inoculation," introduced by Lafargue, nor that proposed by Luton and Bertin, which consists in the injection of irritants into diseased tissues. It is obvious that by the hypodermatic method medicines can be introduced only in the state of solution. To introduce the solution under the skin, a special instrument is necessary. This is the now well-known hypodermatic syringe—a small syringe having a capacity not to exceed a drachm—the nozzle being a hollow needle having a lancet-shaped extremity for easily transfixing the skin. These instruments are various in form and construction, and are made of gold, silver, glass, or hard rubber. The most efficient instrument for ordinary use is the silver hypodermatic syringe described by the author. The piston-rod of this instrument should be semi-cylindrical, and should be graduated for minims on its flat side, to indicate the quantity of solution contained in the barrel. To avoid the ill results which may follow the use of instruments not properly constructed, they are now so made as to be easily rendered aseptic. With an asbestos packing of the piston, and needles that can be sterilized by heat, the danger of local inflammation from the deposit of septic germs is reduced to the minimum. In the instrument devised by Koch, the piston-rod with its packing is dispensed with, and the air for forcing the fluid out is furnished by a rubber air-bag which is attached to the barrel of the instrument. Allen and Hanbury, of London, have lately brought forward an aseptic instrument in which the piston-rod is made to fit accurately the barrel of the instrument, and thus any kind of packing is dispensed with. Numerous models of the hypodermic instrument have been brought forward within the past few years, from which a suitable selection can always be made. Before using any instrument it should be well washed out with boiling water, and, after using, the needle should be dried and the wire inserted. In doubtful cases, the skin at the point where the injection is to be made should be washed well with soap and water, and then bathed in hydrogen-peroxide solution, or some other antiseptic.

A medicine employed for hypodermatic use should be capable of perfect solution in the menstruum, which is usually distilled or pure water. Particles of medicine undissolved are not only not in a condition for ready absorption, but are irritant to the tissues, producing inflammation and abscess. The solution for hypodermatic use should be free from foreign matter of every description and should be neutral in reaction, or, at least, without decided acid or alkaline property. Any substance which will coagulate the blood or produce violent local irritation is unfit for hypodermatic use. A solution of even a neutral substance should not be too concentrated. Clean water, free from visible impurities, is entirely harmless, and the quantity of fluid injected is, within certain limits, a matter of indifference, provided suitable care be used in selecting the site and injecting. On the other hand, concentrated solutions are more apt to produce local irritation than dilute solutions. Moreover, a drop too much of a concentrated solution of a powerful alkaloid may produce an alarming, if not dangerous state. In ordinary syringes a few drops remain at the bottom of the barrel and in the needle—whence it follows, in using strong solutions, it is difficult to inject the precise amount desired.

Solutions of alkaloids, too long kept, become unfit for use hypoder-matically, by reason of the development in them of a penicillium, a minute organism which grows at the expense of the alkaloid. Fresh solutions should be made when needed. When hypodermatic injections are used infrequently, it is preferable to prepare an extempore solution, using powders of a definite strength. Filtered river, melted ice, or rain water, may be used for dissolving the powders. Solutions prepared extemporaneously from ordinary spring or rain water are found to produce less inflammation, and are less likely to be followed by abscess, than solutions prepared with pure distilled water which have been kept for several days. The author, therefore, advises the use of extemporaneous solutions made with powders of suitable strength or the compressed tablets now prepared by the manufacturing pharmacists.

In practicing the hypodermatic injection it is important to avoid puncturing a vein. Serious depression of the powers of life and sudden and profound narcotism have been produced by injecting a solution of morphine directly into a vein. Fatal collapse may ensue from injecting air into a vein along with the narcotic solution. Bony prominences ought to be avoided, and also inflamed parts. It is not necessary to follow Wood, the discoverer of the hypodermatic method, who advised that the solution be inserted at those points where pain can be awakened by pressure (the painful points of Valleix). Some exceptions to this rule undoubtedly exist. The arms, the abdomen, the thighs, the calves of the legs, and the back, are suitable places. Eulenburg makes the assertion that the effect is slower when the injection is made in the back, but I have not observed this difference.