HAHNEMANN science, when a distrust of the received system of therapeutics caused him to pause in his labors. In place of facts and laws, he com- plained that lie found only hypotheses and theories. Finding that he could no longer con- scientiously practise his profession, he returned in 1789 to Leipsic, where he resumed his chemical studies, and endeavored to support his family by translating English and French medical authors. At first he was obliged to struggle with poverty, and his children experi- encing severe attacks of illness, he could only prescribe for them according to a system in which he had ceased to place confidence. This stimulated his desire to establish a new system of therapeutics. In 1790, while engaged upon a translation of Cullen's " Materia Medica," he was struck with the contradictory properties ascribed to Peruvian bark, and the various ex- planations given of its operation in intermittent fever. He resolved to try upon himself the effects of the medicine, and, after several pow- erful doses, discovered symptoms analogous to those of intermittent fever. The fact that a drug had produced upon a man in health the very symptoms which it was required to cure in a sick man immediately suggested to him the law, Similia similibus curantur ("Like cures like "), which is the groundwork of the homoeopathic system. He determined to test the principle fully before announcing it to the world, and experimented upon himself with a variety of drugs. Similar results having been obtained in every instance, and also in experi- ments tried upon others, he applied the new law to the treatment of the patients in the in- sane asylum at Georgenthal near Gotha, over which the duke of Saxe-Gotha had appointed him, with complete success. From Georgen- thal he proceeded to Pyrmont, Brunswick, and Konigslutter, effecting in each place remark- able cures. In 1796, in a paper published in Hufeland's Journal der pralctiscJien Heilkunde, he made his first public exposition of the simi- lia similibus principle, which, if not its dis- coverer, he was the first to declare to be the leading principle in therapeutics. His sugges- tions were received with indifference or ridi- cule, and during the next 15 years he was the object of ceaseless attacks from those whose interests were opposed to the innovations he sought to introduce into medical practice. Du- ring this period he published several works, all treating of the new theory ; among which was Fragmenta de Viribus Medicamentorum Positims sive Obviis in Corpore Sana (2 vols., Leipsic, 1805). But in his Organon der ra- tionellen Heilkunde (Dresden, 1810) homoeopa- thy first received its distinctive name, and was first reduced to a system and methodically il- lustrated. This work created much sensation in Germany, and a bitter warfare was waged for upward of 12 years between the old and new schools of therapeutics. About this time he fixed his residence in Leipsic, where he en- tered upon an extensive practice, and gathered HAIL 379 about him many friends and disciples. During the prevalence of a malignant form of typhus in 1813, caused by the recent presence of the allied and French armies, the patients became so numerous that it was necessary to divide them among the physicians of the city. Of the 73 allotted to Hahnemann, and treated on the homoeopathic method, all recovered except one old man. But this only increased the en- mity of his opponents, and* an old law was re- vived which prohibited a physician from dis- pensing his own medicines, a practice Hahne- mann had always followed, and was unwilling to relinquish. He therefore in 1820 removed to Kothen, where for a time he encountered the same hostility which had driven him from Leip- sic. But the homoeopathic system was mean- while making its way silently over Europe, and patients repaired from all sides to receive the advice of its founder. The importance which the petty town of Kothen thus acquired soon caused a reaction in his favor, and when, upon his marriage for a second time in 1835 with Mile. d'Hervilly, a young French woman, he took his departure, it was deemed necessary to go secretly by night for fear the populace might insist upon detaining him. Repairing with his wife to Paris, he resided there in the active practice of his profession until his death. A statue of Hahnemann was erected in Leipsic in 1851 by the homoeopathic physicians of Ger- many, and another in Berlin in 1855. Besides those already mentioned, his principal works are : Heine Arzneimittellehre (6 vols., Dresden, 1811-'20 ; 3d ed., 1830-'33) ; Die chronischen KrankJieiten (4 vols., Dresden, 1828-'30; 2d ed., 1835-'9) ; and Heilung der asiatischen Cholera (Nuremberg, 1831). A collection of his minor works has been published (2 vols., Dresden, 1829-'34). Several of his works have been translated into English and other lan- guages. (See HOMCEOPATHY.) HAIL, the aqueous vapor of the atmosphere congealed in icy masses, called hailstones, and precipitated upon the earth. Hailstones vary in size and internal structure, from the homo- geneous masses one eighth of an inch in di- ameter forming sleet, to the larger masses 3 in. in diameter, of beautiful crystalline struc- ture, and to the still larger accretions of these masses sometimes a foot or more in diameter. The crystalline structure of most hailstones is remarkably distinct. The centre of the hail is a collection of semi-translucent granules or a spongy mass of snow and opaque ice ; sur- rounding this nucleus is a more or less well defined radiated structure of crystals of ice ; a large quantity of air is always enclosed within the interstices of the hailstone. Occasionally the stones are composed of concentric rings of ice and snow ; when they consist of clear ice without the snowy nucleus, there is almost in- variably found in the centre, in place of the nucleus, a cavity filled with condensed air; from experiments made in 1871 it has been shown that this bubble of enclosed air is sub-
