Troja, Michele

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(b. Andria, Apulia, Italy, 23 June 1747; d. Naples, Italy, 12 April 1827)


Troja studied medicine at Naples and then won a competition for the post of assistant surgeon at that city’s Hospital of San Giacomo degli Spagnoli. In 1774 he obtained a scholarship for postgraduate study that enabled him to go to Paris, where he began the research on the formation of bone callus and bone regeneration that made him famous. For this work, which continued that of Henri-Louis Duhamel du Monceau, he was nominated corresponding member of the Paris Academy and was invited by Diderot to write a number of articles for the supplement of the Encyclopédie.

When he returned home in 1779, Troja was given the chair of ophthalmology at the University of Naples, a post established especially for him, since the subject had not been taught there until then. In the following year he became surgeon of the king’s chamber for having successfully cured the crown prince of a disease. In 1802 Troja campaigned successfully for the creation of a commission to spread the knowledge and use of Jenner’s smallpox vaccination.

Troja is known especially for his studies on the nutrition and regeneration of bones, a subject that was the focus of academic interest at that time. Even Spallanzani became interested in it; and in his letters he referred to the work of Troja, although apparently without great enthusiasm. Such an unfavorable judgment does not appear justified today, for Troja considerably improved the techniques of study. For instance, he used immersion in nitric acid to bring out bone structure and applied zinc sulfate to obtain coloration of the cells and improve the visibility of microscopic structures.

Troja’s research on the eye is preserved in a volume of lectures on eye disease. In urology he studied the diseases of the bladder and of the urinary system in general, and invented the flexible catheter. This invention derived from his active interest in and knowledge of India rubber, which had just been introduced into Europe.

In addition to his own work in anatomy and microscopy, Troja collaborated with G. S. Poli for many years in the latter’s investigations on the anatomy of mollusks.


I. Original Works. Troja’s writings include De novorum ossium in integris aut maxime ob morbis deperditionibus regenratione experimenta (Paris, 1775); Lezioni intorno alle malattie degli occhi (Naples, 1780); Lezioni intorno ai mali della vescica orinaria e delle sue appartenenze . . . Colla giunta di una memoria sulla costruzione dei cateteri flessibili (Naples, 1785–1793); and Osservazioni ed esperimenti sulle ossa; in supplemento ad un’opera sulla rigenerazione delle ossa, impressa nel 1775 (Naples, 1814).

II. Secondary Literature. See M.del Gaizo, “Della vita e delle opere di Michele Troja,” in Atti della R. Accademia medico-chirurgica (Naples), 52 (1899), 191; and 53 (1899), 351; Gianni Randelli, “Ripetizione degli esperimenti di Michele Troja sulla rigenerazione delle ossa,” in Physis, 6 (1964), 45–64; and A. von Schoenberg, Biographie des Dr. und Professor M. Troja (Erlangen, 1828).

Carlo Castellani