Note 91 — THE INDIVIDUAL ORGANISM WITH REGARD TO FORM AND METABOLISM (continued 3)

I only mention here that certain modern psychologists have assigned the true law of Weber to the sphere of judgment and not of sensation. If applied to objective reactions only, in their dependence on objective stimuli, it, of course, becomes less ambiguous, and may, in a certain sense, be said to measure “acclimatisation” with regard to the stimulus in question. The mathematical analogy of the law of Weber to the most fundamental law of chemical dynamics seems very important.

As to “acclimatisation” in the more usual meaning of the word, with regard to a change of the general faculty of resisting certain agents of the medium, “immunity” proper is to form a special paragraph of what follows, and to “acclimatisation” towards different degrees of salinity (in algae or fishes) some special remarks will also be devoted on a proper occasion. There remains only “acclimatisation” to different temperatures; but on this topic not much more than the fact is known (see Davenport, Arch. f. Entw. Mech. 2, p. 227). “Acclimatisation” does not allow of a sharp general definition; it may be the result of very different kinds of adaptations in our sense of the word.