ESSAY XXIV.

ANTIPRAX Y.

"Every step the mind takes, in its progress towards knowledge, makes some discovery; which is not only new but the best too, for the time at least."

JOHN LOCKE.

ESSAY XXIV.1

ANTIPRAXY:2

THE CONTRARY ACTION OF DIFFERENT DOSES OF
THE SAME DRUG IN HEALTH.

"It cannot be doubted that, had we a more intimate acquaintance with, and precise knowledge of, the action of remedies, the therapeutic properties of medicines would no longer appear incomprehensible and mysterious."

JONATHAN PEREIRA.

The

1. WHEN Scientific medicine shall be generally adopted, specific names will not be needed. disappearance of the necessity will be quickly followed by the disappearance of the names.

In the meantime, until this happy result shall be brought about, even scientific medicine is, in a certain sense, sectarian, and specific names are unavoidable. Under these circumstances a name must be given to the law which governs the actions of different doses of the same drug in health. It is now known that the action in health of a certain range of small doses is in the opposite direction to that of a certain range of large doses that the one is contrary to the otherand it is proposed to call this contrary action antipraxy.

1 First published in 1874.

2 avrimpatis, counteraction.-PLUTARCH.

2. The changes in the phenomena of heat, electricity, and magnetism, depend mainly upon the quantity of the force developed.

The changes in the action of the force of gravity depend upon distance and quantity.

While those in chemical action are governed by quality and quantity; a different weight of each element being required in order to be combined by chemical affinity with other elements.

Drug action resembles the last. The changes in its effects are dependent upon quality and quantity.

Now, no settled principles were discovered in chemistry till the balance was carefully used by Mr. Cavendish and others.

And if we would discover the principles of drug action, and arrive at any hopeful precision in the administration of drugs as medicines, we must not only observe their qualitative action-the effects produced by each drug by itself, both in health and disease—but we must undertake a careful investigation into the action of different doses, or quantities, of the same drug, as well in health as in disease. As measurements are important in mechanics, and weights in chemistry, so success in therapeutics depends very much upon doses.

The qualitative action of each drug has already, to a great extent, been discovered by experiments in health.

The quantitative action of different doses of each drug has waited to be discovered by similar experiments with them in health.

This is the only way in which the endless conflicts on the question of doses can be terminated, and the indescribable confusion in which it has hitherto existed be reduced to order.

3. From the experiments on the action of small doses in health, detailed in a former Essay, it has appeared that, in different doses each drug has not one kind of action only, but two; and that these two kinds

of action are in opposite directions to each other. It will be useful to pursue the subject further.

The first consideration which arises is the question of analogy. Is the fact just stated a solitary phenomenon? or, is it supported and rendered probable by other operations in nature which offer points of analogy with this remarkable law of the dose?

Reflection will discover some analogous conditions. It will have been noticed that one feature of the phenomenon is a dividing line. Of this we have a striking analogy or illustration in a magnetized steel bar. In this, it is well known, there is a neutral centre, from each side of which proceed magnetic forces, opposite in their tendencies, one force repelling what the other attracts.

The other feature of the phenomenon is, that a smaller quantity acts in one way, and a larger in the opposite way. Chemical affinity gives us some analogous examples of this:-oxygen and manganese combine in different fixed proportions; one equivalent of each forms a salt-making base—that is, an oxide which combines with acids to form salts; three equivalents of oxygen and one of manganese unite to make an acid-which combines with alkalies to form salts. No two things in chemistry are more opposite than a base and an acid. There are other instances, though this is not known as a general law of such combinations at present it seems rather a rudimentary fact.

The action of heat furnishes more extended analogies. For example—a certain amount of heat effects the combination of some chemical elements, and a larger amount of it causes the decomposition of the compounds the smaller amount of it had produced. Here the making of compound bodies, and the unmaking of them, is due to the action of the same agent in different quantities. The two elements already mentioned are examples of this also; manganese and oxygen, with a moderate amount of heat readily unite and form oxides; and one of these oxides, when