This system of medication was introduced by Dr. Alexander Wood, of Edinburgh, in 1843.

A great number of syringes for this purpose are on the market, but the three principal types are the all metal solid piston, the all-glass Syringe, and that having a glass barrel with a leather-packed piston. The first is the cheapest, the second the most expensive.The first has the disadvantage that its contents cannot be seen; the second the disadvantage that it is easily broken. A well-made syringe of the third variety is the most satisfactory all-around instrument.

In preparing the syringe for use the medicament, almost invariably in the tablet form, may be dissolved within the barrel of the syringe, or external to it. If the former method is used, draw warm boiled water into the syringe and drop in the tablet, and nearly :all tablets will be completely dissolved in from five to twenty seconds. If it be preferred to dissolve the tablet external to the syringe, a teaspoon may be used in which the measured water and the tablet are boiled together. After the syringe has been filled screw on the needle and with the syringe vertical, the needle end upmost, push in the piston until all air is expelled. The instrument is now ready for use.

The skin should be cleaned before introducing the needle, and this may be done with alcohol, or a little hot water. The skin should then be pinched up between the thumb and forefinger of one hand while the other hand introduces the, needle into the fold of skin so pinched, at a slight angle to the surface of the body. If thrust rapidly and the needle is sharp, clean and perfectly beveled, there is almost no sensation. The piston should then be depressed, steadily, but not too slowly, until the content of the barrel is expressed. If injection is made too rapidly the tissues are distended with such rapidity as to cause pain, while if it is done rather slowly there need be but little discomfort. The site of the injection is of little importance. Avoid, however, the following: the neighborhood of large vessels and nerves, surface veins, the thinly covered bones, and especially sensitive or inflamed regions. The best situations are the arm near the insertion of the deltoid muscle and the inner surface of the thigh, though the region of the biceps muscle, the forearm and calf of the leg are often used.