Homoeopathy , (Gr. Homoeopathy 0800526 like, and Homoeopathy 0800527 to be affected), a system of medicine first definitely propounded by Hahnemann. (See Hahnemann, Samuel.) Its cardinal principle, from which it derives its name, is expressed in the aphorism, Similia similibus curantur, "Like cures like;" that is, the proper medicines to be administered in disease are those which produce similar symptoms in a healthy person. This principle had been partially enunciated by Hippocrates, the "father of medicine" (about 460 B. C.), who asserted that medicines sometimes acted according to the rule of similia, and at others according to that of contraria ; thus intimating the truth of both the allopathic law of contraria and the homoeopathic law of similia. Antiphanes, who lived about the same time, wrote a poem which contains the earliest known announcement of the homoeopathic theory. Galen (born A. D. 130), the first great light in medical history after Hippocrates, first gave form and shape to that law of contraria which for many centuries ruled the medical world.

Starting up, however, from time to time, during the centuries which intervened between Hippocrates and Hahnemann, were Paracelsus, Stahl, Haller, and others, who insisted upon the truth of the law similia, and pushed their investigations with more or less success in that direction ; but it was not until it attracted the attention of Hahnemann that it created much attention, or assumed the definite form of an important law in medical science. Hahnemann at the age of 35 occupied a prominent position as a scholar and chemist. While translating (1790) into German Cullen's "Materia Medica," the passage in which Cullen describes the action of cinchona bark excited his curiosity as to how this substance acted in curing ague. By way of experiment he took four drams of it in different doses, being at the time in perfect health. In a few days he experienced all the symptoms of ague. Was this ague, he inquired, the result of the action of the cinchona, or did it arise from the usual causes of the disease? There were two ways of testing this matter.

One was to examine collections of reported cures, in order to ascertain whether among them any notice was to be found of instances in which the remedy employed was known to possess the property of exciting symptoms in the healthy similar to those which it cured in the sick. The other was to ascertain by experiment what was the effect of medicinal substances when taken by those in health, and then to administer them to those who were ill, and whose illness presented symptoms similar to those caused by these substances. The result of his historical researches is given in the "Introduction to the Organon of Medicine." He collected from an immense variety of sources testimony in regard to the twofold action of more than 30 medicinal substances; and one set of authorities proved the power of a certain drug to produce symptoms similar to those reported by other authors to have been cured by the very same means. Medical works in the present time are full of similar illustrations. For example, in the "Cyclopae-dia of Practical Medicine," edited by Forbes, Tweedy, and Connolly, we read, under the head of Fever: "Arsenical solution is the anti-periodic medicine on which, next to quinine, most reliance may be placed." One of the recognized authorities on the subject of ague is Dr. Boudin, who, after quoting a similar experience by M. Biot, says: "For my part, I saw an intermittent quotidian fever supervene, which I was obliged to combat with quinine, in a patient to whom I had given for ichthyosis about five grains of arsenic in twelve days." This occurred when there was no ague in the place.

Thus, on the one hand, we have arsenic producing the disease, and on the other curing it. Dr. Copland, editor of the "Dictionary of Practical Medicine," says: " Ipecac is one of the best remedies that can be resorted to for asthma;" and Dr. Pereira, the author of the great work on materia medica, says: "In asthma benefit is obtained from ipecac in small and repeated doses." Sir John Forbes, one of the most distinguished physicians of his time, says: "Practitioners of experience, without subscribing to the doctrine of homoeopathy, will certainly think more favorably of ipecac on account of its peculiar tendency to induce fits of asthma in the predisposed." This direct antidote to asthma is known to cause asthmatic attacks in many persons. "How singular," says Dr. Marshall Hall, "that ipecac taken into the bronchia should excite asthma." " If I remain in a room," says Mr. Koberts of Dudley, " where the preparation of ipecac is going on, I am sure to have a regular attack of asthma." Sulphur cures peculiar forms of eruptive diseases; and all frequenters of the baths of sulphurous waters are acquainted with its effects in producing similar eruptions.

Laennec, the discoverer of the stethoscope, says of tartar emetic : " From its use we sometimes find patients, doomed to almost certain death, out of all danger after the lapse of a few hours, without having experienced any evacuation or change but the rapid and progressive amelioration of the disease." Dr. Williams, a celebrated medical author, says: " Next to blood-letting tartar emetic is the most powerful remedy we can employ for the cure of acute pulmonary inflammation." Tartar emetic, according to these writers, and very general experience, cures pulmonary inflammation. The great French physiologist Magendie made this drug the subject of special experiment. After describing other changes it produced in animals which he poisoned with it, he says: "It acts specifically in inflaming the lungs." M. Pelletrier, who has written the best monograph on this drug, says : " Its effect on the respiratory organs is to produce difficulty of breathing in dogs; the lungs were found hepatized. One would imagine that, admitting its action in man to be similar, far from being useful, its administration would be particularly pernicious in the treatment of pneumonia." - For several years Hahnemann seemed to be groping among specifics before he discovered the key to their successful administration.

Medicines were given at first in massive doses, which, notwithstanding they generally cured the patient, sometimes produced fearful aggravations. At length, after a long course of experiment, the idea became firmly established in his mind that the organism through disease became exceedingly susceptible to the action of a drug given in accordance with the law of similia, and whose action was that of a direct specific on the diseased part. In 1799 an unusually fatal epidemic of scarlet fever prevailed at Konigslut-ter. Hahnemann, guided by the law of similia, selected belladonna as the appropriate remedy, administering it in minute doses; the curative effect was marked and decided. In 1801 his experiments with belladonna in scarlet fever were published at Gotha, and created much interest and no little opposition in Germany. In the same year he published a reply to the objections raised against his statements on the ground that so small a dose must be powerless, in which he says: "To the ordinary practitioner it is incredible that a person when sick is violently affected by a millionth part of the same drug that he swallowed with impunity when he was well.

Will physicians ever learn how infinitely small may be the dose that is sufficient for a cure, when the system of the patient is raised to a condition of intense and morbid sensitiveness? So powerfully do such small quantities act upon the over-sensitive frame, that the most serious disease is sometimes subdued in a few hours." Dr. Jorg, one of the most distinguished 'opponents of Hahnemann, says: "Medicines operate most powerfully on the sick when their symptoms correspond to the disease. Where there is inflammation of the intestines, a very minute dose of mercury will produce pain and other symptoms. It is in the very nature of things that a medicine must have a much greater effect when administered to a person already suffering under an affection similar to that which the medicine is capable of producing." Photography, according to homoeopaths, presents a striking illustration of this idea. The healthy body, they say, may be compared to the plate before it has been washed, when it reflects the rays of the sun without its surface being at all affected by his influence; and the unhealthy body to the same plate washed by a chemical process, and thus rendered so sensitive to light that the faintest ray makes on it an indelible impression. - Thus far Hahnemann's knowledge of the specific action of medicine had been derived mostly from his collection made from medical history.

But this, although sufficient to establish in his mind the truth of the law of similia, was not sufficiently accurate to serve as a foundation upon which to build the structure of a thoroughly scientific system of therapeutics. In 1805 he published a work on the positive effects of medicine and the effects produced by them on the healthy body, containing his observations upon 25 substances, most of them powerful vegetable medicines, in which their toxicologi-cal action, as shown by actual experiment on the healthy living body, is minutely described. In conducting his experiments, the substance to be tested was distributed among his assistants, who each took a succession of doses and carefully recorded the symptoms. These were compared with his own; and several years after, when the same drugs were re-proved by a society at Vienna, every one of the observations of Hahnemann was confirmed. In 1831 the cholera first invaded Europe. In Hungary 8,000 died out of 10,000 who were seized. Medicine seemed powerless, and the consternation was universal. Hahnemann, guided by his law of similia, selected camphor as the appropriate remedy to be given at the first onset of the disease; and experience has since justified the wisdom of his selection.

Other remedies were pointed out in the different stages of cholera, but the usefulness of camphor, given according to Hahnemann's directions, is now generally admitted. - To be guided intelligently by the law of similia, the keynote of their system, homoeopathists believe we must have an accurate picture of the pathological changes resulting from the drug as indicated by the appearance of tissues after death, and its action as shown upon the living structure in vivisection. For this the most careful observation is required - not only the selection of cases of accidental poisoning, and others from historical records and daily practice, but the actual placing of the system under the direct action of the drug, and the careful noting of each individual symptom. Hence has arisen the plan of "proving" medicines, as inaugurated by Hahnemann, and which they claim as the only correct basis of a true scientific materia medica. Their materia medica is made up of drugs so tested by several observers, and the symptoms corresponding noted as the characteristic ones of the drug. Growing out of this law, as a natural sequence, and forming the second grand division of the system, is that of the dynamization of medicines.

The system having become sensitively acute to the action of a drug, this, when given homoeopathically, or in accordance with the law of similia, should be given in a dose so minute as only to act on the part morbidly susceptible. If given in too large doses, so as to produce its primary or drug action, no relief would be obtained, but harm might ensue; while if given in too small doses, no action whatever would result. Hence the importance not only of the homoeopathic selection of the remedy, but its administration in doses of only sufficient strength to produce its tonic or curative action. The homoeopath insists upon the positive purity of his drugs, and in those of a vegetable character usually prefers the expressed juice, discarding the inert material. By the process of dynamization, in which the particles are more completely broken and subdivided, it is believed the latent power or life of the drug is often set at liberty, and materials which in their crude state are almost inert are found to possess a strong influence as remedial agents. Thus mercury or quicksilver in its crude state has no medicinal action; but when its particles are subdivided by trituration with a non-medicinal substance, the conserve of rose, we get blue mass, or blue pill, whose power is well known.

So, in the preparation of homoeopathic attenuations, the crude drug, carefully divested of impurities, is triturated thoroughly with a non-medicinal substance, sugar of milk, or dissolved in alcohol or distilled water. One grain of the crude drug triturated with nine of sugar of milk, or dissolved in nine drops of alcohol, forms the first decimal attenuation; and one part of the drug combined with 99 of the sugar of milk or alcohol forms the first centesimal attenuation. To get the second decimal or centesimal, one part of the first is combined with 9 or 99 parts of the non-medicinal substance; and so on through the successive steps of the process. The first step is to select the drug homoeopathic to the disease, and give it either in its crude form or in its attenuation, as best seems to meet the exigencies of the case. - What homoeopaths claim as cardinal principles are: 1. The law of similia, or the treatment of disease by medicines whoso effects, tested on the living, healthy organism, are similar to the symptoms present in disease.

They do not claim this principle as universal or exclusive, since medicines are often required for their mechanical, nutritive, and chemical effect; but they assert that it is of great value, and, when carefully considered and correctly applied, gives when indicated the most satisfactory results. 2. They assert that the law of similia demands an intimate knowledge of the effect of the drug upon the healthy organism. The question of dose is left to the individual judgment of the practitioner; but when given in accordance with the law of similia it is found that a greatly reduced dose gives the most satisfactory results. The homoeopathic doctrine, as above stated, admits of a wide diversity on minor points. Some in this school confine themselves to the high potencies; but the majority range in their prescriptions from the crude drug up through what are called the lower potencies; all however admitting, as the keystone of the system, the law of similia. - In 1825 homoeopathy was introduced in the United States by Hans B. Gram, a native of Boston, but educated in Copenhagen. His success attracted the attention of several physicians, among whom were Gray, Channing, Willson, Hall, and Hering. A careful study of the principles of the new theory secured their adherence; and its success, not only in ordinary diseases, but in usually fatal epidemics, soon won for the system a large support.

In the United States the school now (1874) numbers about 6,000 physicians. There are nine homoeopathic colleges, which at the session of 1872-'3 graduated 204 students. Every college has a dispensary connected with it for clinical teaching, and five have flourishing hospitals; and there are 32 dispensaries not connected with any college. There are 31 hospitals and asylums under the charge of this school. - The school, for its age, is rich in practical literature. Among the important works are: Hahnemann's Organon, Materia Medica Pura, and "Chronic Diseases;" Hartmann's "Acute and Chronic Diseases;" Jahr's Symptomen-Codex or "Manual of Materia Medica;" Bonninghausen's "Therapeutics;" Baehr's " Theory and Practice;" Grauvogel's " Practice;" E.Guernsey's "Practice;" H. H. Guernsey's "Obstetrics;" Dudgeon's "Lectures;" Hempel's "Materia Medica;" Helmuth's "Surgery;" and Franklin's "Surgery." There are also published in the United States 13 periodicals devoted to homoeopathy.