This was the commencement of our more modern ideas regarding digestive proteolysis, but only the commencement, for it ushered in an era of unparalleled activity, in which Brücke, Schützenberger, and Kühne each contributed a large share toward the successful interpretation of the results obtained. Further, knowledge regarding the proteid-digesting power of the pancreatic juice was rapidly accumulating, thus broadening our ideas regarding digestive proteolysis in general. Corvisart[18] had called attention to the proteolytic power of the pancreatic juice in 1857, and although his observations were more or less generally discredited for a time, they were eventually confirmed by Meissner,[19] Schiff, Danilewsky,[20] and Kühne,[21] the latter particularly contributing greatly to the development of our knowledge concerning this phase of digestive proteolysis. The proteolytic power was proved to be due to a specific ferment or enzyme, now universally called trypsin, which digests proteid foods to the best advantage in the presence of sodium carbonate. Digestive proteolysis in the human body was thus shown to be due mainly to the presence of two distinct enzymes, the one active in an acid fluid, the gastric juice, the other in an alkaline-reacting fluid, the pancreatic juice, but both endowed with the power of digesting all varieties of proteid foods, with the formation of a large number of more or less closely related products. [18] Sur une Fonction peu connue du Pancréas: La digestion des aliments azotés. Paris, 1857-58. [19] Verdauung der Eiweisskörper durch den pankreatischen Saft. Zeitschr. f. rat. Med., 3d ser., Band 7, p. 17. 1859. [20] Virchow’s Archiv, Band 25, p. 267. 1862. [21] _Ibid._, Band 39, p. 130. 1867. So much for the early history of our subject, and now, without attempting any exhaustive sketch of its gradual development during the last decade and a half, allow me to present to you digestive proteolysis as it stands to-day, developed somewhat, I trust, by the results I have been able to contribute to it during the last twelve years. THE GENERAL NATURE OF PROTEOLYTIC ENZYMES.