have access, putrefying fluids, like protoplasm, are able to oxidize completely the most resistant substances, side by side with strong reductions. Hoppe-Seyler noticed that if animal substances be allowed to putrefy in vessels deprived of air, intense reductions ensue, hydrogen gas is often set free, and the whole chemical transformation is entirely different from that which the same substances undergo if a current of air be constantly forced through the fluid. In the latter case the transformations are oxidations, and finally are of a most complete kind, little else than nitrates, carbonates, and sulphates being left. If a putrefying fluid be allowed to stand exposed to air, Hoppe-Seyler discovered that at the surface the most intense oxidation ensued, while in the depths there were equally intense reductions. He found, further, in studying the fermentation of fibrin and calcium lactate, as well as other substances, that if no oxygen were present large quantities of hydrogen gas were evolved, if air were present no hydrogen was evolved. He immediately recognized in nascent hydrogen a reducing agent capable of causing the strong reductions and of splitting the oxygen molecule, thus indirectly causing oxidation. He suspected that nascent hydrogen would combine with one atom of the oxygen molecule to form water, setting the other atom free, and experiment fully confirmed this hypothesis. If palladium be heated in a stream of hydrogen, it combines with the latter. If it now be brought into water, the hydrogen is liberated in the atomic state. Hoppe-Seyler found that palladium loaded with hydrogen would carry out oxidations and reductions similar to those of putrefying fluids. If such a palladium mass be half immersed in water containing benzol, hæmoglobin, potassium iodide, or indigo, in the depths of the fluid strong reductions ensue, with at the surface equally violent oxidations. In such circumstances oxyhæmoglobin at the surface is transformed into methæglobin, benzol to phenol, indigo to indigo white at the bottom and indigo yellow at the surface, and iodine is liberated from its potassium combination. Hoppe-Seyler believed that in protoplasm a substance was present which acted somewhat like potassium hydrate or the ferments in the putrefying masses, causing a saponification, and at the same time a transference of an oxygen atom from a hydrogen to a carbon atom, with the liberation of nascent hydrogen, or other reducing substance. The nascent hydrogen, in the manner already indicated, caused both intense reductions as well as oxidations. In this manner, as is well known in chemical processes outside of the cell, many syntheses and polymerizations can be brought about, and it would seem necessarily to result, in protoplasm, in just such a constant rearrangement of molecules as is imagined constantly to be transpiring there. Hoppe-Seyler believed that the oxygen