It has been believed for over two thousand years that like remedies could cure disease, that is to say, that Belladonna which produces poisoning symptoms closely similar to an attack of scarlet fever, could cure that illness. Century after century such treatment had its advocates but it was always successful. In 1790, Hahnemann tested out on himself the action of Cinchona bark (crude quinine) to ascertain its pure effects. He developed symptoms closely resembling a paroxysm of malaria. Here was a remedy which was capable of producing in health a clinical picture identical with the disease for which it was almost a specific remedy. After many other experiments on himself and friends with Cinchona bark and other drugs, Hahnemann confirmed that there was a relationship between the therapeutic application of a drug and its effect in health, and that by testing or proving drugs on healthy human beings, this could be used as a reliable guide to their effect in disease. Hahnemann did more than merely give confirmation to an ancient belief which was only partly true; he discovered why like remedies sometimes worked and at other times failed. Perhaps the best way to explain this is to take primary pneumonia and consider the matching of a like remedy. There are always two groups of symptoms in pneumonia, firstly, those such as cough, pain in the chest, dyspnoea and cyanosis, which can be explained by the presence of an inflamed mass of lung tissue; secondly, there is a group of symptoms which are largely disregarded outside of homoeopathic practice, as they are of little or no importance when chemotherapy is used. The second group of symptoms varies from patient to patient, although there is a tendency to follow a limited number of patterns. One child for example is irritable, thirsty and likes to be left undisturbed, another likes the nurse to hold her hand, wants cold milk to drink and is afraid of the dark and of being left alone. These symptoms have appeared since the onset of the pneumonia and disappear when the patient is recovering, yet they are not the direct result of pneumonic process. It is reasonable to suppose that these symptoms represent in some way, just as fever does, the patient’s response, the attempt to get well. It is these symptoms which are matched in homoeopathic prescribing by a drug which could call forth a similar reaction in health. In other words the pattern of response is observed and an antigenic stimulus given, specific to the individual. Bryonia is the homoeopathic prescription for the first case and Phosphorus for the second. If the diseases were measles or typhoid fever and these responses were observed, the same remedies would be given in homoeopathic practice. Belladonna is the correct homoeopathic treatment for scarlet fever when there is a close similarity between the clinical picture and Belladonna effects. It is not the remedy if the patient exhibits a different clinical picture. Sulphur is more frequently indicated today. The prescription, however, is based on the individual clinical picture and will only be successful when it covers the individual expression of the disease.