The terms Therapeutics and Treatment, although, they may at first sight appear too simple to call for analysis, are found, on careful consideration, to include four different notions. These we must study individually.

1. Health

Health. The first notion involved in Treatment is a purely physiological one, the conception of health, or the normal state, from which the organ has departed, and to which it has to he restored. Health is the result of a number of natural influences acting on the individual, namely, the extrinsic circumstances around him., and the intrinsic conditions which he brought into the world with him. Our organs having reached their present state by a process of evolution under the influence of the various natural forces which surround us, are obedient to these influences; and when a definite change is thus produced upon them, we call it the "physiological action" of the influence. The first point for the therapeutist to appreciate is, that just as the forces which surround us are themselves constantly varying-the various conditions of the temperature, the air, our food, in short our whole environment, being inconstant-so the physiological state of the body is not a constant quantity. We speak of a "normal" state, and call it "health," but the first essential of life and health is power of change and accommodation to varying circumstances.

2. Pharmacodynamics: Physiological action. - The second elementary notion in the expression "treatment" is, that we possess a certain power of interference, a control over the conditions and circumstances of life, and thus a certain control over the health or physiological state of the individual. A very little consideration will enable us to appreciate our power over the forces of nature. Most of the influences we have just considered as normal in their effects, and many that are entirely morbid in character, are within our control. We can alter the food we eat, the air we breathe, our clothing, our sources of heat; we may admit into our bodies substances which we find in nature-mineral, vegetable, animal, or altogether artificial. On the other hand, we may voluntarily shun or reject such substances, and avoid many influences, whether for good or for bad, around us. To express this control which we have over our organs and functions, through the conditions to which we can voluntarily subject them, we say we act physiologically upon them, by such and such means, or that such and such a substance has such and such a physiological action ; and the science that relates to this power which we possess of modifying physiological activity we call Pharmacodynamics.

3. Pathology

Pathology. The conception of disease is also included in "treatment." When the conditions which surround us become unusual or extraordinary, they lead to disturbance of the vital processes. If this be moderate, it is still included under the name of "health;" but if considerable, it is called disorder or disease, and the influence is called a morbid influence. It is essentially impossible to draw a line between health and disease, just as it is impossible to divide influences into salutary or physiological, and morbid or pathological. The pulse is accelerated by joy, by wine, by fever; which of these conditions is health, which disease ? All that can be said is, that the change from the normal state is frequently so definite that we cannot reasonably call it "health," that we must find another name for it, and call it "disorder;" or if it be more marked, and attended by. suffering, "disease."

4. Recovery

Recovery. Successful treatment necessarily involves a power of recovery. The body possesses abundant provisions for preventing disease, and of recovering from its effects. This power of meeting and overcoming morbid influences depends essentially on the great physiological law which we have already noticed, that the activity of the tissues and organs is not fixed and constant, but varies (within certain limits) with the conditions to which it is subjected. The body is abundantly provided with the following means by which this variation of functional activity can be secured:

First, when occasion demands it, the organs can display an extraordinary amount of force, as we see in the case of a muscle such as the biceps, or the heart. The organs thus possess a certain amount of reserve force, which is frequently called into play as a means of preventing disease. But for this, we should break down in every part of our body as often as we made an extra demand upon it.

Secondly, if this reserve force be constantly called into play by the continuance of some extraordinary cause, the increased activity gives rise to enlargement or hypertrophy of the organ, and what is known as compensation is the result. This great natural method of prevention or recovery by overcoming the cause of disorder is well seen in heart disease, and in enlargement of one kidney when the other is diseased.

Instead of themselves meeting extraordinary circumstances by extraordinary activity, many organs are provided with regulating mechanisms, by which they can throw them off or escape from them, that is, expel the cause of disorder. The stomach rejects a heavy or improper meal; the heart can, to some extent, relieve itself of excessive peripheral resistance in systole, through the depressor mechanism; and the body heat is elaborately regulated by various nervous arrangements.

Thirdly, the work of one organ may sometimes he undertaken by another organ, which thus removes the effects of the disorder. This is called vicarious compensation, and is well seen at work between the kidney and other excretory organs.

Fourthly, even when disease and anatomical change have actually occurred, the body possesses means of recovery of the nature of repair, which is associated with nutritive activity and frequently with the inflammatory process.

These considerations teach us that just as our organs and functions continue normal, like everything else in nature, in obedience to the laws under which they have reached their present form, so, if they have become deranged by unusual influences, they will return to the normal when such abnormal influences have been overcome or removed.