in that they show us the superiority of oxydative to that of the anoxydative disintegration in the cell economy. This is of particular interest when we consider those organisms in which great demands are made upon the capability of movement, above all, in homothermous forms, the metabolism of which takes place on a continuously high level. For this reason, in homothermous animals the respiration of oxygen is the almost exclusive source of energy production. [59] _A Pütter_: “Der Stoffwechsel des Blutegels (Hirudo medicinalis L).” I Theil. Zeitschrift für allgemeine Physiologie Bd. VI, 1907. II Teil. ebenda Bd. VII, 1908. The previously mentioned facts make it clear that in one and the same form of living substance both oxydative and anoxydative decomposition processes are found, depending upon the conditions. This does not apply merely to the individual organic forms, such as the facultative anaërobic organisms, but generally to all aërobic living substance. If oxygen is withdrawn from an aërobic organism the disintegration does not cease in consequence. In place of the oxydative we have anoxydative decomposition. The various aërobic organisms are, however, adapted in very different degrees to the possibility of an anaërobic existence. While the facultative anaërobic organisms can continue to exist without oxygen, the homothermous animals become asphyxiated in a very short time in the absence of oxygen, in that they are poisoned by the products of the anoxydative decomposition, which are eliminated with much more difficulty than carbon dioxide and water. The fact, however, that disintegration also continues in an anoxydative form, if oxygen is withdrawn, has given rise to the thought, which has been accepted especially by plant physiologists with great readiness, that the decomposition of organic respiratory substances of the aërobic organisms invariably takes place in two stages; in that the dextrose molecule--to again use this as an example--is split up first by an enzyme into larger fragments, which then in the second stage of the process undergo combustion to the formation of carbon dioxide and water. Such a possibility cannot be repudiated. I wish, however, to state that one should be very reluctant in generalization of this assumption for all aërobic organisms. The types of metabolism in the different organisms are so manifold and of such immense variety that we should be very careful in our generalizations before being in possession of material extending over a great number of groups of organisms. Above all, it does not seem justifiable to also accept this type for life existing at higher temperatures, and still less to apply it to those instances in which the production of energy following stimulation is suddenly increased to great amounts. Let us suppose that the disintegration process occurs in two phases, the first of which after the type of the fermentation of dextrose separates