[93] Rubner, Die Gesetze des Energieverbrauches bei der Ernährung, Leipzig u. Wein, 1902.
[94] The phenomenon of fever we leave out of account here; it is regarded by some as regulation, by others as a disturbance of heat regulation. Of course, if the first view should ever prove to be the right one, fever might be classified among the real regulations of the secondary type.
[95] Jahrb. wiss. Bot. 36, 1901.
[96] Carbohydrates cannot be ionised, and therefore there is no doubt that in von Mayenburg’s experiments the organism itself is actively at work. As to compounds liable to ionisation, it has been noticed by Maillard that a certain regulatory character is contained simply in the physical fact that the degree of ionisation changes with concentration: decrease of concentration for instance would be followed by an increase of ionisation, and so the osmotic pressure may be preserved (C. rend. Soc. Biol. 53, 1901, p. 880).
[97] In the different experiments of Nathansohn (Jahrb. wiss. Bot. 38, 1902, and 39, 1903) the salinity of the medium was changed in such a way that there was in each case either an abnormal increase or an abnormal decrease in the concentration of one single ion necessary for metabolism. The cell was found to stand these abnormal changes in such a way that in the case of the increase of the concentration of the medium it did not allow more than a certain amount of the ion in question to come in, and that in the case of the decrease it did not allow more than a certain quantity of the ion to go out. It thus seems as if the permeability of the surface were adjusted to a certain minimum and to a certain maximum of every single ion or salt, the permeability being stopped from within to without, whenever the minimum, and from without to within, whenever the maximum is reached in the cell sap; both irrespective of proper physical osmotic equilibrium (“Physiologisches Gleichgewicht”). Thus, in fact, there only would be a case of primary regulation, nothing more. It would all appear rather similar to what occurs in the kidney. Of course we do not assert that our explanation is right, but it is possible and is at the same time the most simple, and it is our general practice always to prefer the most simple hypotheses.
[98] Many fishes are able to withstand great changes in the osmotic pressure of sea-water; the osmotic pressure of their body fluids, though never in a real physical equilibrium with the pressure of the medium, nevertheless may vary whenever the abnormal conditions of the latter exceed certain limits.
[99] See Stahl, Naturw. Wochenschrift, N. F. 5, 1906, No. 19.
[100] Arch. Anat. Phys., Phys. Abt. Suppl., 1902.
[101] The adaptive phenomena discovered by Gaidukow depend upon a real alteration in the formation of pigments. In the (primary) chromatic adaptation of pupae of Lepidoptera with respect to the colour of the ground they live upon, we only have the variable effects of pre-established chromatophores (Poulton, Phil. Trans. London, 178 B, 1888; Merrifield, Trans. Ent. Soc. London, 1898). The same holds for chromatic adaptations in crabs (Gamble and Keeble, Quart. Journ. Micr. Sci. 43, 1900; Minkiewicz, Arch. Zool. exp. et gén. sér. 4, 7, notes, 1907).
[102] The theory of oxidation we have shortly sketched here was developed in chapter B. 5, of my Organische Regulationen. Recent discoveries of Winterstein’s (Zeitschr. allg. Physiol. 6, 1907) have given the strongest support to my hypothetic statements, and, in fact, can be said to have brought the doctrine of organic oxidation to a critical point. There can be no doubt that oxygen not only plays the “antipoisonous” rôle I had assigned to it, but that it is not even of such great importance for the supply of functional energy as former times had assumed. No doubt it serves to drive the functional machine, but decomposition of certain chemical constituents of the organism serves this purpose even more. The latter does so in the most fundamental and original manner, so to speak, whilst oxidation only burns up its products. Almost all elemental functions, in nerve-tissue at least, go on very well in the absence of oxygen, provided that certain “poisonous” substances, resulting from this anaërobic metabolism, are constantly removed. In normal conditions that is done by oxygen, and in doing so oxygen certainly assists the supply of energy, but it does not furnish the whole of it. The difference between so-called “aërobic” and “anaërobic” life almost completely disappears under such a view, and many so-called “regulations,” of course, disappear at the same time; there is no more “intramolecular respiration.”