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ON THE NATURAL FACULTIES Book I
[p. 35] this law,
Lit. "necessity" ; more restrictive, however, than our "law of Nature." cf. p. 314, note 1.
every animal needs several organs for altering the nutriment. For in order that the yellow may become red, and the red yellow, one simple process of alteration is required, but in order that the white may become black, and the black white, all the intermediate stages are needed.
His point is that no great change, in coours or in anything else, can take place at one step.
So also, a thing which is very soft cannot all at once become very hard, nor vice versa; nor, similarly can anything which has a very bad smell suddenly become quite fragrant, nor again, can the converse happen.
How, then, could blood ever turn into bone, without having first become, as far as possible, thickened and white? And how could bread turn into blood without having gradually parted with its whiteness and gradually acquired redness? Thus it is quite easy for blood to become flesh; for, if Nature thicken it to such an extent that it acquires a certain consistency and ceases to be fluid, it thus becomes original newly-formed flesh; but in order that blood may turn into bone, much time is needed and much elaboration and transformation of the blood. Further, it is quite clear that bread, and, more particularly lettuce, beet, and the like, require a great deal of alteration, in order to become blood.
This, then, is one reason why there are so many organs concerned in the alteration of food. A second reason is the nature of the superfluities.
Not quite our "waste products," since these are considered as being partly synthetic, whereas the Greek perittomata were simply superfluous substances which could not be used and were thrown aside.
For, as we are unable to draw any nourishment from grass, although this is possible for cattle, similarly we can derive nourishment from radishes, albeit not