Pharmacotherapy. - This includes the study of remedial agents proper or the use of drug substances. It considers the applications of the teachings of pharmacology to the treatment of abnormal body states. It naturally constitutes the most important branch of therapeutics.

It is not to be supposed that our present elaborate systems of pharmacotherapy have come into existence as they now are found. They have had a natural development, and the various methods have merged, the one into another. Certain arbitraiy methods have received special names, such as Empirical, Specific, Statistical, Physiological, Rational Therapeutics, etc.

Empirical Therapeutics implies the application of remedies to which experience has ascribed certain specific properties irrespective of systematic value. It is not based upon experimental research, but rather upon formulae established by the accumulation of isolated facts - empiricism - and practical observation, apart from theoretical reasoning and the relations of physiological phenomena as revealed by modern methods of investigation. Were it possible to extend indefinitely the list of remedial agents so as to embrace the entire field of therapeutic knowledge, the empirical method might attain the dignity of an exact science. Such, however, is the complexity arising from the manifold, often contradictory, impressions drawn from human experience that for the evolution of a systematic scheme of therapeutics the empirical system must of necessity prove inadequate.

By Specific Therapeutics is meant a system of treatment that implies that certain diseases have certain definite antidotes. Thus, mercury and the iodides are specifics for syphilis, antitoxin for diphtheria, antivenin for snake-bite, etc.

Statistical Therapeutics implies a method of treatment that is the outcome of the experience of the results observed in a large number of cases under certain restricted lines of treatment. This method arrives at excellent results if sufficient numbers of cases of the same type can be observed, but disease processes vary so widely in different individuals that the statistical method alone is not unlikely to lead to error.

Physiological Therapeutics consists in the application of the strict interpretations of the pharmacodynamic action of drugs to diseased conditions. With increasing knowledge its principles will prove more and more applicable, but the inherent difficulties of interpretation of all biological phenomena will always make this method unsatisfying.

Rational Therapeutics is a term much in use, but it means simply an application of the various criteria, empirical, statistical, experimental, etc., in the treatment of diseased processes. The rationalist cares less for the name of the disease and more for the disturbance of general organic functions, not isolated symptoms, but group symptoms, which indicate some large functional disturbance.

On the General Action of Drugs. - Broadly speaking, the action of drugs is exerted either locally or systemically, whereas the effects which are known as reflex action occupy a middle ground between the two. Many drugs have only a limited action at the point of application, while others possess not only a local, but a systemic, action as well.

The action of drugs is fundamentally a question of protoplasm chemistry, but the investigations of the biologist have not yet reduced the interpretations of nature to a question of molecular physics; until they do, pharmacology will retain the words irritation, stimulation, depression, paralysis, and death of protoplasm.

Hueppe, in 1891, enunciated the doctrine that all remedies first, in small doses, produced an irritant and stimulating action in protoplasm, to be followed, when used in larger doses, by a depressing or paralyzing action, which might go on to death of the protoplasm acted on. Thus the effects of small and large doses were contrasted; the foundations of the homeopathic idea are closely related to this interesting phenomenon. It is not a universal phenomenon, however, and cannot be designated as a law, as Hueppe claimed. There are a large number of substances that in small and large doses have antagonistic effects, but the antagonism is by no means an equal one. Thus is it a familiar illustration that small doses of morphine increase mental activity by slight stimulation, whereas large doses depress and paralyze and bring about unconsciousness. The grade of excitement cannot at all be made commensurate with the grade of depression by making the doses smaller and smaller. Chloral acts as an irritant to the peripheral nerve-endings, although it depresses and paralyzes the central nervous system. Citations might be multiplied to show the host of inconsistencies and variations.

If such variations are found to be true for the action of drugs on the normal human body, how much more variable are the results of pharmacotherapy on the diseased organism. At times a given agent acts with less force on a diseased organ than on a healthy one; at times again with greater activity, and still further the action of a drug may vary widely in health and in disease.

At the present time the limits of present-day information offer but little hope for a better interpretation of these questions, and not only is the clinical side of the problem obscure, but the chemical side is equally uncertain. It seems that different chemical actions must be considered. Many compounds seem to react on protoplasm with a mutual disarrangement of the molecules; thus the action of strychnine is interpreted; others act on the tissues and are eliminated unchanged, and yet have probably altered the chemical character of the tissues acted on. Of late years, through the studies of followers of Nernst and Ostwald, an entirely new series of studies have been carried on which are destined to be closely related to the study of the physiological action of drugs. The study of electrolytic dissociation has already opened up new fields in physiology, and the ground is being broken in pharmacology. In the salts of the alkalies are found a series of actions differing from those already spoken of; here the active agent induces changes in the watery content of the protoplasm or in the water of the liquids surrounding the cells, and brings about a series of physical, rather than chemical, changes. The familiar experiments of plasmolysis in the botanical laboratories illustrate this action, which is controlled by the general laws of diffusion of liquids, which are separated by animal or vegetable membranes.