The knowledge of what drugs will do when given to a healthy subject can be utilized in two different ways, both legitimate, and it is a mere matter of experience and observation to determine which is the better. We can use a drug to produce its physiological effects. If this is desired, the drug must be given in a dose large enough to produce symptoms - that is, in a so-called physiological dose, differing with each drug and determined by experiment. This is the antipathic use of drugs, and has nothing to do with Homoeopathy, or the law of cure. It is, moreover, very limited in its application, and objectionable on many grounds.

The other method, the homoeopathic relationship, is universal in its application, and is not confined to any special dosage, provided such always is sub-physiological - i. e., less than is required to produce symptoms. Hence, drugs can act in two different ways when given in disease, and we can have, therefore:

1. Homoeopathic relationship - when given for conditions similar to those they are capable of producing. Applicable to all drugs, and universal in its extent.

2. Antipathic or allopathic relationship - when given in physiological dosage to produce their first, direct or physiological effects. This is, as we have stated before, of but very limited application.

The only difference in the application of drugs to disease with the two schools of medicine is, that the old school gives drugs solely to obtain their direct, physiological effects, and rather favors combination of remedies, while the homoeopathic school depends entirely upon the curative results obtained by giving the single remedy in a sub-physiological dose for symptoms similar to those it is known to produce.

For reference and further study, see Hahnemann's Essay on a New Principle for Ascertaining the Curative Powers of Drugs in his Lesser Writings, page 249.

Hahnemann's Essay on the Sources of the Common Materia Medica, being Preface to Vol. II of the Materia Medica Pura.

The Physiological Action of Medicines, by Wm. Sharp, in Essays on Medicine, page 417.

General Principles of Drug Action, by R. Hughes, in Pharmacodynamics; lecture IV-V.

An interesting account and practical application of the Doctrine of Signatures can be found in Grauvogl's Textbook, § 91-95.

Samuel A Jones, M.D.: "The Grounds of a Homoeopath's Faith". An inspiring little work.

Dudgeon. "Lectures on Homoeopathy". Lect. VI, Isopathy.