the acceleration of the functional constituent parts of metabolism produced by the stimulus bringing about the formation of carbon dioxide and water. The question arises: _By what means is the particular labile state of just this constituent part of functional metabolism conditioned?_ The lability of the functional portion of metabolism, excitated by the stimulus, resembles the processes in the disintegration of explosive combinations. Iodide of nitrogen, for instance, in a manner similar to the living substance in the state of the metabolism of rest, constantly disintegrates even without the influence of an impact. The disintegration is suddenly enormously increased by the result of a jar. An explosion follows. In a like manner the functional metabolism of rest is explosively excitated by the stimulus, the transformation of the energy involved likewise bears a similar relation. In both instances the transformation of energy, _constant_ in the resting state, is by the impact of the stimulus suddenly increased. The dynamic method of investigation of the excitation process with its physical indicators, forms, therefore, in many respects an excellent addition to the chemical analysis. A development, that is, exothermic formation, of energy can only occur in a chemical process when the chemical affinities which are to be combined are stronger than those which have been separated. When this process is brought about by a simple impact, the energy value of which bears no relation to that of the quantity of energy in the process itself and which occurs with explosive rapidity, then it can be simply a question of a liberation process, that is, a process by which the impact brought about a conversion of latent chemical energy into that of kinetic energy. The comparison of the functional excitation process with that of an explosion does not, therefore, consist in a merely superficial analogy, but is founded on the same dynamic principles. When we study the chemical process which occurs in the explosive transformation of potential into kinetic energy we find two types of chemical processes. The first type includes the synthetic processes. For this, the synthesis of water from explosive gas may serve as a simple example. Here the weaker affinities in comparatively simple molecules (H + H and O + O) are separated and stronger affinities are combined in the formation of more complicated molecules (H + O + H). The second type represents the process of cleavage. As example for the latter, the explosive disintegration of nitroglycerine may be quoted. Here the atoms, held together in a complex molecule by weaker affinities, are changed by transposition of nitroglycerine. For instance, the hydrogen atoms loosely combined with carbon enter into strong combinations with oxygen and the oxygen loosely combined with the nitrogen enters into strong combination with carbon, so that water and carbon dioxide are formed and nitrogen and oxygen set free. [Illustration]