Organs and tissue, which are cut off from all food supply through the blood and lymph, may remain active for many hours. _H. v. Baeyer_[64] has shown that the ganglion cells in the frog, in which saline solution was transfused at room temperature and containing no trace of organic substances and where irritability has been increased to the maximal by means of strychnine, were capable of strenuous work for nine or ten hours before losing responsivity. The nerves and muscles of the animal retain their excitability for even a longer period under the same conditions. Indeed, we have histological evidence of the existence of organic reserve material in the various cells in the form of embedded bodies in the protoplasm. As for instance the disappearance of the _Nissl_ granules in the ganglion cells following great activity,[65] (Figure 12), or that of the granules in infusoria cells during starvation.[66] (Figure 13.) We assume that a certain amount of organic foodstuffs in a state properly prepared is present in the cell. As the amount of these prepared substances is consumed, new quantities of stores, having undergone various preparatory processes, among which the enzymic actions may be considered to play a chief rôle, are brought into that form in which they appear suited to fill the gap produced by disintegration. Plant physiologists in particular have here again furnished us with some essential data for the assumption of the existence of such processes which regulate the transformation of reserve substances as well as its extent. _Pfeffer_[67] has found in several fungi and bacteria that there exists a compensation between the diastatic breaking down of the carbohydrates stored as reserve material and the quantity of dextrose introduced. He further found that the more the reserve substance is split up into dextrose the less of the latter is introduced from without and _vice versa_. _De Bary_[68] some time ago also observed in the _bacillus amylobacter_ an analogous relation between the enzymatic cellular digestion and the quantity of dextrose introduced with the food. An equilibrium, therefore, exists between the required amount of dextrose and the extent of enzymic splitting up processes of the reserve material. A great number of similar processes have been observed. Even though the details of the whole preparatory assimilative processes are beyond our knowledge we can still say with certainty that, on the one hand, everywhere great quantities of organic reserve substances are always present in the cell, and on the other, that these substances are subjected to a transformation into suitable material for building-up processes, the extent of which is controlled according to need, by the processes of self-regulation. [64] _H. v. Baeyer_: “Zur Kenntniss des Stoffwechsels in den nervösen Centren.” Zeitschr. f. allgem. Physiol. Bd. I, 1902.