Book 3
15
Moreover, of the two vessels connected with it, that which brings pneuma into it from the lungsHe means the left auricle, considered as the termination of the pulmonary arteries; cf. p. 314, note 3. is much smaller than the great outgrowing arteryThe aorta, its orifice being circular, appears bigger than the slit-like mitral orifice. from which the arteries all over the body originate; this would suggest that it not merely gets pneuma from the lungs, but that it also gets blood from the right ventricle through the anastomoses mentioned.
15
Now it belongs to the treatise On the Use of Parts to show that it was best that some parts of the body should be nourished by pure, thin, and vaporous blood, and others by thick, turbid blood, and that in this matter also Nature has overlooked nothing. Thus it is not desirable that these matters should be further discussed. Having mentioned, however, that there are two kinds of attraction, certain bodies exerting attraction along wide channels during diastole (by virtue of the principle by which a vacuum becomes refilled) and others exerting it by virtue of their appropriateness of quality, we must next remark that the former bodies can attract even from a distance, while the latter can only do so from among things which are quite close to them; the very longest tube let down into water can easily draw up the liquid into the mouth, but if you withdraw iron to a distance from the lodestone or corn from the jar (an instance of this kind has in fact been already givenp. 87.) no further attraction can take place.
