This section is from the book "A Compend Of The Principles Of Homoeopathy", by William Boericke. Also available from Amazon: A Compend of the Principles of Homoeopathy as Taught by Hahnemann.
Homoeopathy discovered the fact that there is an opposition in effects between very large and small doses. A teaspoonful of wine of Ipecac, causes sickness and vomiting, while drop doses cure the same. Large doses of Opium bind up the bowels, while a small dose has the opposite effect. Large doses of Bryonia act as a drastic, while small have a tendency to promote a torpid state of the intestines. This physiological antagonism between large and small doses of drugs is one explanation made use of in regard to the homoeopathic law.