In December 1820 he went to Rome as travelling physician to his likely godmother Elizabeth, now Duchess of Devonshire. He afterwards attended her in that city during her fatal illness in March 1824. On his return to London he was appointed physician to
Napoleon I at St. Helena, but the emperor died (on 5 May 1821) before he left England. In July 1821 he commenced practice at Naples, and his social gifts made him popular with all the English residents there, who included Sir
William Gell, Sir
William Drummond, and the
Countess of Blessington. At Naples, too, Quin met Dr. Neckar, a disciple of
Samuel Hahnemann, the founder of homeopathy, and was favourably impressed by what he learned of the homeopathic system of medicine. After visiting Leipzig in 1826, to study its working, Quin returned to Naples a convert. On the journey he was introduced at Rome to
Prince Leopold of Saxe-Coburg, afterwards king of the Belgians, and soon left Naples to become his family physician in England. Until May 1829 he continued a member of the prince's household either at Marlborough House, London, or Claremont, Surrey, and extended his acquaintance in aristocratic circles. From May 1829 to September 1831 he practised in Paris, chiefly, but not entirely, on the principles of Hahnemann. In September 1831, after consulting with Hahnemann as to the treatment of cholera, he proceeded to Tischnowitz in Moravia, where the disease was raging. He was himself attacked, but soon recommenced work, and remained until the cholera disappeared. His treatment consisted in giving camphor in the first stage, and ipecacuanha and arsenic subsequently. At length, in July 1832, he settled in London at 19 King Street, St. James's, re- moving in 1833 to 13 Stratford Place, and introduced the homeopathic system into this country. The medical journals denounced him as a
quack, but he made numerous converts, and his practice rapidly grew, owing as much to his attractive personality as to his medical skill. But the professional opposition was obstinately prolonged. In February 1838, when Quin was a candidate for election at the
Athenæum Club, he was opposed by a clique of physicians, led by
John Ayrton Paris, who privately attacked Quin with a virulence for which he had to apologise. From 26 June 1845 he was medical attendant to the
Duchess of Cambridge. In 1839 Quin completed the first volume of his translation of Hahnemann's
Materia Medica Pura, but a fire at his printers' destroyed the whole edition of five hundred copies, and failing health prevented him from reprinting the work. In 1843 he established a short-lived dispensary, called the St. James's Homœopathic Dispensary. In 1844 he founded the
British Homeopathic Society, of which he was elected president. Chiefly through his exertions the
London Homeopathic Hospital was founded in 1850. It became a permanent institution, and is now located in Great Ormond Street. On 18 October 1859 he was appointed to the chair of therapeutics and
materia medica in the medical school of the hospital, and gave a series of lectures. Quin was popular in London society. In aristocratic, literary, artistic, and dramatic circles he was always welcome. He was almost the last of the wits of London society, and no dinner was considered a success without his presence. His friends included
Charles Dickens,
William Thackeray, the Bulwers, Macready, Landseer, and
Charles Mathews. In manners, dress, and love of high-stepping horses he imitated
Count D'Orsay. After suffering from severe and chronic asthma and arthritis, which resulted in retirement from medical practice, he died of bronchitis at the Garden Mansions, Queen Anne's Gate, Westminster, on 24 November 1878, and was buried in
Kensal Green Cemetery on 28 November. ==Works==