Bonneval returned to France where he completed his medical studies at Montpellier and in 1835 defended the first medical thesis in France on homeopathy, dedicating it to Hahnemann in recognition of his genius.
Bonneval opened a thriving homeopathic medical practice in Bordeaux and was an active member of the La Société Homoeopathique Gallicane (French Homeopathic Society) serving as a vice president at the 1855 French Homeopathic Medical Congress in Paris.
He was assistant manager of the Strasbourg stud farm in 1830, when Louis-Philippe, an Orleanist, ascended to the throne of the Bourbon Charles X. As several other legitimists, Count Henri refused to take an oath to the new king and prefered to resign his position.
Interested in medicine, he was deeply impressed by Hahnemann‘s Organon der Heilkunst and decided to leave France for Köthen, in Saxony, in order to learn homeopathy directly from its founder. Back to France, he defended in Montpellier the first French medical thesis devoted to homeopathy and then opened a consulting room in Bordeaux. He rapidly gained a solid reputation and a large audience as a practitioner of homeopathy.
At the same time, Henri acquired the Chateau de Latresne and the 500 acres surrounding land. He renovated and brought up to date the agricultural and wine-producing activities of the estate. The medical doctor soon proved to be an expert agronomist, extending his competence to the famous vineyard Chateau Canon of St. Emilion.
Throughout his life, the Count showed notable qualities of philanthropy, materialized at Latresne by the construction of a church and, adjacent to the chapel, a boarding school, two classrooms and shelters for poor or sick old people. At the end of his life, Henri de Bonneval wrote a comprehensive book, that includes the presentation and discussions of the homeopathic methods, some philosophical reflections and personal memories.
The Bibliothèque Homoeopathique for 10 July, 1882, contained the following obituary:
“We have lost one of the veterans of our old guard – Comte Henri de Bonneval, who was taught by Hahnemann himself in the principles of our new doctrine. He died at his chateau, La Tresne, near Bordeaux.”
His graciousness, scientific renown and charity had given him for years an exceptional position in his vicinity.
It was about 1825 or 1826 that he completed his preparatory studies.
He was arrested in his career by a malady which even threatened his life, and cured against all expectation by a celebrated physician who had introduced a new and strange method ; he decided to study medicine and embrace the doctrine by which his health had been restored.