The author, after referring to the late researches of Mulder, Vogel, Liebig, &c, whose experiments proved the close analogy between albumen, fibrin, and casein, and their almost identity in composition, stated that, in consequence of some experiments he had performed a few years ago, he was led to entertain the idea that all the animal fluids and solids consist of modifications of one and the same prototype animal matter. The following considerations seemed to confirm this opinion.