The Oxford Dictionary defines magic as ' the pretended art of influencing the course o f events by compelling the agency of spiritual beings (black magic) or by bringing into operation some occult controlling principle of nature (white magic) '. The great gaps in our knowledge of disease, coupled with the patient's demand that all disease shalI receive treatment in spite of our ignorance, insure the survival of many practices falling within this definition of white magic. But in the dawn of medicine it was black magic that predominated. To primitive man illness is a mysterious occurrence without any obvious cause ; his earliest explanation was the belief that an evil spirit had entered into the sufferer and his first attempts at treatment were directed to driving the demon out. Our oldest medical treatise is the Ebers papyrus, found in Egypt a century ago but dating from the reign of Amen-hetep I of the 18th dynasty (about 1550 B.c.). The Smith papyrus is even older but is mainly concerned with surgical conditions. The Ebers papyrus prescribes invocations to be uttered when taking a dose of medicine: ' Come remedy, come drive it out of this my heart, out of these my limbs ' ; ' Oh demon who dwellest in the body of . . . son of . . . come forth.' These invocations have their modern counterpart in the Latin imperatives and the symbols, deliberately unintelligible to the layman, which the doctors of today are trained to append to their prescriptions. And the numerous medicines mentioned in this pharmacopoeia are of a highly obnoxious character, emetics and purges, calculated to make the body of the patient SO unpleasant an abode for the resident demon that he would be glad to quit if not forcibly ejected with the physical evacuations. Lizards, stinking fat, the excreta of human beings, donkeys, dogs and cats, putrid meat, are all prescribed. Castor oil and mandragora are listed amongst the herbal remedies. The belief that a medicine must be nasty to be beneficial though now obsolescent in England lasted to our own day: Gregory's powder and other nauseous remedies remain vivid memories of the older generation and historically they owe their origin to their unpleasantness.