instrument, and an act having motion; as in works of art the instruments are moved, for in them, in some sort, the motion of the art exists."
By these words he seems to imply, that generation is owing to the motion of a certain quality. Just as in art, though the first cause (the "ratio operis") be in the mind of the artist, yet afterwards, the work is effected by the movement of the hands or other instruments; and although the first cause be removed (as in automatons,) yet is it in some sort said to move what it now does not touch, but once has touched, so long as motion continues in the instrument.
Also in the next book, he says: "When the semen of the male has arrived as far as the uterus of the female, it arranges and coagulates the purest part of the excrement (meaning the menstrual blood existing in the uterus); and, by a motion of this kind, changes the material, which has been prepared in the uterus, till it forms part of the chick; and this, hereafter, although the semen after the performance of this motion disappears, exists as part of the fœtus, and becomes animate (as the heart,) and regulates its own powers and growth, as a son emancipated from his father, and having his own establishment. And so it is necessary that there be some commencing principle, from which afterwards the order of the limbs may be delineated, and a proper disposition made of those things that concern the absolution of the animal; a principle, which may be the source of growth and motion to all the other parts; the origin of all, both similar and dissimilar parts, and the source of their ultimate aliment. For that which is already an animal grows, but the ultimate aliment of an animal is the blood, or something corresponding to the blood, whose vessels and receptacles are the veins; wherefore, the heart is the origin of the veins. But veins, like roots, spread to the uterus, and through these the fœtus derives its nourishment. The heart too, being the beginning of all nature and the containing end, ought to be made first; as if it were a genital part by its own nature, which, as the original of all the other parts, and of the whole animal, and of sense, must needs be the first; and by its heat, (since all the parts are in the material potentially,) when once the beginning of the motion has taken place, all that follows is excited, just as in spontaneous
