The parenteral introduction of various drugs has of late years become more and more common. Such injections, however, have the disadvantage that the drug effect is transitory, for, irrespective of the mode of injection, the medication reaches the blood stream relatively quickly and its effect is soon over. This drawback is, of course, not significant under some conditions, as the use of a narcotic to deaden pain, or of a stimulant during collapse. For many other purposes, however, as with glandular preparations, continuous action is much to be desired.
The transitory effect of hypodermic medication is well shown by two drugs, epinephrine and camphor. Figure 1 illustrates the effect on blood pressure of three injections of 1 cc. each of epinephrine given during a period of four hours. It will be noted that each injection was followed by a rise in the blood pressure, but that this rise was of