And, from another point of view, even if it were true, it is superfluous, if the stomach[171] has the power of compressing the veins, as he himself supposed, and the veins again of contracting upon their contents and propelling them forwards.[172] For, apart from other considerations, no _plethora_[173] would ever take place in the body, if delivery of nutriment resulted merely from the tendency of a vacuum to become refilled. Now, if the compression of the stomach becomes weaker the further it goes, and cannot reach to an indefinite distance, and if, therefore, there is need of some other mechanism to explain why the blood is conveyed in all directions, then the principle of the refilling of a vacuum may be looked on as a necessary addition;[174] there will not, however, be a plethora in any of the parts coming after the liver,[175] or, if there be, it will be in the region of the heart and lungs; for the heart alone of the parts which come after the liver draws the nutriment into its right ventricle, thereafter sending it through the _arterioid vein_[176] to the lungs (for Erasistratus himself will have it that, owing to the membranous excrescences,[177] no other parts save the lungs receive nourishment from the heart). If, however, in order to explain how plethora comes about, we suppose the force of compression by the stomach to persist indefinitely, we have no further need of the principle of the refilling of a vacuum, especially if we assume contraction of the veins in addition--as is, again, agreeable to Erasistratus himself. BOOK II B I