On Generation and corruption   

flesh and converts it into actual flesh. The acceding food, therefore,

must be together with the growing thing: for if it were apart from it,

the change would be a coming-to-be. For it is possible to produce fire

by piling logs on to the already burning fire. That is 'growth'. But

when the logs themselves are set on fire, that is 'coming-to-be'.

'Quantum-in-general' does not come-to-be any more than 'animal'

which is neither man nor any other of the specific forms of animal:

what 'animal-in-general' is in coming-to-be, that 'quantum-in-general'

is in growth. But what does come-to-be in growth is flesh or bone-or a

hand or arm (i.e. the tissues of these organic parts). Such things

come-to-be, then, by the accession not of quantified-flesh but of a

quantified-something. In so far as this acceding food is potentially

the double result e.g. is potentially so-much-flesh-it produces

growth: for it is bound to become actually both so-much and flesh. But

in so far as it is potentially flesh only, it nourishes: for it is

thus that 'nutrition' and 'growth' differ by their definition. That is

why a body's' nutrition' continues so long as it is kept alive (even

when it is diminishing), though not its 'growth'; and why nutrition,

though 'the same' as growth, is yet different from it in its actual

being. For in so far as that which accedes is potentially 'so

much-flesh' it tends to increase flesh: whereas, in so far as it is

potentially 'flesh' only, it is nourishment.

The form of which we have spoken is a kind of power immersed in

matter-a duct, as it were. If, then, a matter accedes-a matter,

which is potentially a duct and also potentially possesses determinate

quantity the ducts to which it accedes will become bigger. But if it

is no longer able to act-if it has been weakened by the continued

influx of matter, just as water, continually mixed in greater and

greater quantity with wine, in the end makes the wine watery and

converts it into water-then it will cause a diminution of the quantum;

though still the form persists.