Book 1
10
For I believe that I shall prove that the organs which have to do with the disposal of the nutriment, as also their faculties, exist for the sake of this nutritive faculty. For since the action of this facultyThe activation or functioning of this faculty, the faculty in actual operation. cf. p. 3, note 2. is assimilation, and it is impossible for anything to be assimilated by, and to change into anything else unless they already possess a certain community and affinity in their qualities, Un rapport commun et une affinitè (Daremberg). Societatem aliquam cognationemque in qualitatibus (Linacre). cf. p. 36, note 2. therefore, in the first place, any animal cannot naturally derive nourishment from any kind of food, and secondly, even in the case of those from which it can do so, it cannot do this at once. Therefore, by reason of 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.
