BOOK THREE

 [p. 319]full of water and sand, and suck the air out of the tube with your mouth, the sand cannot come up to you before the water, for in accordance with the principle of the refilling of a vacuum the lighter matter is always the first to succeed to the evacuation.

PART 15

is not to be wondered at, therefore, that only a very little [nutrient matter] such, namely, as has been accurately elaborated- gets from the stomach into the arteries, since these first become filled with lighter matter. We must understand that there are two kinds of attraction, that by which a vacuum becomes refilled and that caused by appropriateness of quality;

The "mechanical" principle of horror vacui contrasted with the "physical" or semi-physiological principle of specific attraction. Appropriateness here might almost be rendered affinity or kinship. cf. note 2, infra.

air is drawn into bellows in one way, and iron by the lodestone in another. And we must also understand that the traction which results from evacuation acts primarily on what is light, whilst that from appropriateness of quality acts frequently, it may be, on what is heavier (if this should be naturally more nearly related

"Related," "akin." cf. p. 36, note 2

). Therefore, in the case of the heart and the arteries, it is in so far as they are hollow organs, capable of diastole, that they always attract the lighter matter first, while, in so far as they require nourishment, it is actually into their coats (which are the real bodies of these organs) that the appropriate matter is drawn

The coats exercise the vital traction, the cavities the merely mechanical. cf. p. 165, note 2.

. Of the blood, then, which is taken into their cavities when they dilate, that part which is most proper to them and