As a member of this committee, he signed a decree suspending the performances of Marie-Joseph Chénier's tragedy, Charles IX, or St. Bartholomew's day.

[9] On January 8, 1791, Dumangin acquired the "Château de Rubelles" in Saint-Prix, a village of 515 inhabitants north-west of Paris in the Montmorency valley.

[5] Dumangin bought other property by dispossessing the former lord of Saint-Prix, François Nicolas Le Bas du Plessis (1740-1819).

[5] On 28 July 1794, the representative of the people Paul Barras was charged by the Comité de Salut public to visit Louis XVII, last male prisoner of the Temple[nb 3].

On June 7, Dumangin saw the patient for the first time and found that he was extremely weak, had swollen joints, all the symptoms of lymphatism with chronic diarrhoea.

The patient died the next day 8 June 1795 (20 prairial year III) probably from ulcero-caseous peritonitis of hematogenous origin during chronic disseminated tuberculosis.

[1] The act reads as follows:"Death certificate of Louis Capet, of the 20th of this month, three hours after noon, aged ten years and two months, born in Versailles, department of Seine-et-Oise, domiciled in Paris at the Tours du Temple, section du Temple, son of Louis Capet, last king of the French and Marie-Antoinette-Josèphe Jeanne of Austria.

[11][12][13] He wrote: The day in the Temple this twenty-first Prairial of the third year of the French Republic one and indivisible, at half past eleven in the morning.We, the undersigned, Jean-Baptiste-Eugénie Dumangin, chief doctor of the hospice de l'Unité, and Philippe-Jean Pelletan, chief surgeon of the Grand Hospice de l'Humanité, accompanied by the citizens Nicolas Jeanroy, former professor at the medical schools of Paris, and Pierre Lassus, professor of forensic medicine at the Paris School of Health, whom we joined by virtue of an order of the General Safety Committee of the National Convention, dated yesterday, and signed by Bergouien, President, Courtois, Gaultier, Pierre, Guyomar; for the purpose of proceeding together to open the body of the son of the deceased Louis Capet, and to ascertain its condition, have acted as follows: Arriving every four of us at eleven o'clock in the morning at the outer gate of the Temple, we were received there by the commissioners, who introduced us into the tower.

The aforementioned commissioners told us that this child had died the day before, at about three o'clock in the morning; on which we tried to verify the signs of death, which we found to be characterised by universal pallor, the cold of the body, the stiffness of the limbs, the dull eyes, the ordinary purple spots on the skin of a corpse, and above all by putrefaction beginning in the belly, scrotum and inner thighs.We noticed, before we opened the body, a general thinness, which is that of the marasmus; the belly was excessively stretched and meteorised.

The stomach presented the same condition; it was adherent to all the surrounding parts, pale on the outside, with small lymphatic tubercles, similar to those on the surface of the intestines; its inner membrane was healthy, as were the pylorus and the oesophagus; the liver was adherent by its convexity to the diaphragm, and by its concavity to the viscera which it covers; its substance was healthy, its volume ordinary, the vesicle of the gall poorly filled with a dark green bile.

The spleen, pancreas, kidneys and bladder were healthy; the omentum and mesentery, devoid of fat, were filled with lymphatic tubercles similar to those mentioned.

After forty years of service in the hospital, Dumangin retired in 1820 at Saint-Prix, Val-d'Oise, near Montmorency, where he died on 28 March 1826 at the age of 82 without obtaining the Legion of Honour.