He showed in 1876 that the ammoniacal fermentation of urine is due to a "soluble ferment" (enzyme) which can act in the absence of the living organism to which "one" then attributed the causal role.Musculus, "Sur le ferment de l'urée", Comptes rendus de l'Académie des sciences, vol. 82, 1876, pp. 333-336, online. Pasteur, who had identified the living organism in question ("organized ferment") and attributed to it the role of agent of fermentation, was convinced by the experience of Musculus, but insisted on the fact that the "soluble ferment" was a production of the "organized ferment".L. Pasteur, with the collaboration of J. Joubert, "Sur la fermentation de l'urine", published several times in 1876; Œuvres complètes de Pasteur, vol. 6, p. 80-84, online The discovery of Musculus (the fact that a fermentation is only indirectly caused by a living organism and that it is possible to obtain this fermentation in the absence of this living organism, with the help of non-living substances that it secreted) was, in the particular case of the ammoniacal fermentation of urine, the confirmation of a general conjecture that Moritz Traube in 1858M. Traube, Theorie der Fermentwirkungen, Berlin, 1858, pp. 7–8. Reprinted in Moritz Traube, Gesammelte Abhandlungen, Berlin, 1899, p. 74, point 21 (reprint. Classic Edition, VDM Verlag Dr Müller, 2007). Quoted in English translation by Joseph S. Fruton, Fermentation Vital or Chemical Process?, Brill, 2006, p. 57, online. and Berthelot in 1860M. Berthelot, "Sur la fermentation glucosique du sucre de canne", Comptes rendus de l'Académie des sciences, vol. 50, 1860, p. 980-984, spec. 983-984, where Berthelot conjecturally extends to all fermentations what he observed in the inversion of cane sugar; online. Quoted by Jean Jacques: Berthelot. Autopsie d'un mythe, Belin, 1987, p. 150 and 280. See also André Pichot, introduction to the chapter on fermentations in: Louis Pasteur, Écrits scientifiques et médicaux, Choix, présentation et notes par André Pichot, Paris, Flammarion, pp. 47-48. had formulated about all fermentations and that Buchner would demonstrate in 1897 in the case of alcoholic fermentation. The enzyme discovered by Musculus was later called "urease".William Robert Fearon, "Urease", Biochemical Journal, 1923, xvii, pp. 84-93, spec. p. 84, online.
