## Regulation In Biological Systems

### Survival

10/5.[cont.]   Now regard the system as one of parts in communication.  In the previous section the diagram of immediate effects (of cat and mouse) was (or could be regarded as)

We are now considering the case in which the diagram is

in which $E$ is the set of essential variables, $D$ is the source of disturbance and dangers (such as $C$) from the rest of the world, and $F$ is the interpolated part (shell, brain, etc.) formed by the gene-pattern for the protection of $E.$  $(F$ may also include such parts of the environment as may similarly be used for $E\text{'s}$ protection — burrow for rabbit, shell for hermit-crab, pike for pike-man, and sword (as defence) for swordsman.)

For convenience in reference throughout Part III, let the states of the essential variables $E$ be divided into a set $\eta$ — those that correspond to “organism living” or “good” — and $\text{not-}\eta$ — those that correspond to “organism not living” or “bad”.  (Often the classification cannot be as simple as this, but no difficulty will occur in principle;  nothing to be said excludes the possibility of a finer classification.)

### Reference

• Ashby, W.R. (1956), An Introduction to Cybernetics, Chapman and Hall, London, UK.  Republished by Methuen and Company, London, UK, 1964.  Online.

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