Yet are we not therefore to think that this visible material world attends the nod of the disobedient angels, but rather the power is given them of God. Nor are we to suppose that such evil angels have creative power, but by their spirituality they know the seeds of things which are bidden from us, and these they secretly scatter by suitable adaptations of the elements, and so they give occasion both to the whole being, and the more rapid increase of substances.
For so there are many men who know what sort of creatures use to be generated out of certain herbs, meats, juices and humours, bruised and mingled together in a certain fashion; save only that it is harder for men to do these things, inasmuch as they lack that subtlety of sense, and penetrativeness of body in their limbs dull and of earthly mould.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de Trin., iii, 8