The further criticism to be expected concerns certain verbal imperfections in the definition, which it seems impossible to avoid. It may fairly be urged that the word _correspondence_ will not include, without straining, the various relations to be expressed by it. It may be asked:--How can the continuous _processes_ of assimilation and respiration correspond with the _co-existence_ of food and oxygen in the environment? or again:--How can the act of secreting some defensive fluid correspond with some external danger which may never occur? or again:--How can the _dynamical_ phenomena constituting perception correspond with the _statical_ phenomena of the solid body perceived? The only reply is, that we have no word sufficiently general to comprehend all forms of this relation between the organism and its medium, and yet sufficiently specific to convey an adequate idea of the relation; and that the word _correspondence_ seems the least objectionable. The fact to be expressed in all cases is that certain changes, continuous or discontinuous, in the organism, are connected after such a manner that in their amounts, or variations, or periods of occurrence, or modes of succession, they have a reference to external actions, constant or serial, actual or potential--a reference such that a definite relation among any members of the one group, implies a definite relation among certain members of the other group. § 30. The presentation of the phenomena under this general form, suggests that our conception of Life may be reduced to its most abstract shape by regarding its elements as relations only. If a creature's rate of assimilation is increased in consequence of a decrease of temperature in the environment, it is that the relation between the food consumed and the heat produced, is so re-adjusted by multiplying both its members, that the altered relation in the environment between the quantity of heat absorbed from, and radiated to, bodies of a given temperature, is counterbalanced. If a sound or a scent wafted to it on the breeze prompts the stag to dart away from the deer-stalker, it is that there exists in its neighbourhood a relation between a certain sensible property and certain actions dangerous to the stag, while in its body there exists an adapted relation between the impression this sensible property produces, and the actions by which danger may be escaped. If inquiry has led the chemist to a law, enabling him to tell how much of any one element will combine with so much of another, it is that there has been established in him specific mental relations, which accord with specific chemical relations in the things around. Seeing, then, that in all cases we may consider the external phenomena as simply in relation, and the internal phenomena also as simply in relation; our conception of Life under its most abstract aspect will be--_The continuous adjustment of internal relations to external relations_.[18]