‘Il primo endocrinologo’: Paolo Mantegazza and the Theory of Internal Secretion

During the 1860s, both Charles-Édouard Brown-Séquard and Paolo Mantegazza pondered a proto-endocrine theory of semen being taken up into the blood, which would have androgenic effects. Mantegazza’s nomination as the foremost intellectual precursor to Brown-Séquardism, widely heard in Italy from the 1890s to the 1920s, is animated by the following three observations: (1) during the 1860s Mantegazza with his assistant Giulio Bizzozero undertook various testicular transplantation and reportedly even semen injection experiments and was acquainted, albeit faintly, with the more famous 1848/9 transplantation study by Arnold Berthold; (2) a subsequent conversation between Mantegazza and Charles Darwin over sexual selection pitted Mantegazza’s proto-endocrinology against Darwin’s evolutionary explanation of secondary sex traits; (3) Mantegazza’s theory hardly influenced his sanitarian texts and within his lifetime found only limited acknowledgement by Italian and German authors.