Kata men gar tas artêrias hikanôs enarges to toiouton, hôsper kai kata tên kardian te kai ton thôraka kai ton pneumona. toutôn gar hapantôn diastellomenôn te kai systellomenôn enallax anankaion, ex hôn heilkysthê ti proteron, eis tauth' hysteron ekpempesthai. kai tautên ara tên anankên hê physis progignôskousa tois en tê kardia stomasi tôn angeiôn hymenas epephyse kôlysontas eis toupisô pheresthai tas hylas. all' hopôs men touto gignetai kai kath' hontina tropon, en tois peri chreias moriôn eirêsetai deiknyntôn hêmôn ta t' alla kai hôs adynaton houtôs akribôs kleiesthai ta stomata tôn angeiôn, hôs || mêden palindromein. eis men gar tên 204 artêrian tên phlebôdê, kai gar kai tout' en ekeinois deichthêsetai, poly pleon ê dia tôn allôn stomatôn eis toupisô palin anankaion epanerchesthai. to d' eis ta paronta chrêsimon, hôs ouk endechetai ti tôn aisthêtên kai megalên echontôn eurytêta mê ouk êtoi diastellomenon helkein ex hapantôn tôn plêsion ê ekthlibein authis eis tauta systellomenon ek te tôn êdê proeirêmenôn en tôde tô logô saphes an eiê kax hôn Erasistratos te kai hêmeis heterôthi peri tês pros to kenoumenon akolouthias edeixamen. XIV And further, it has been shown in other treatises that all the arteries possess a power which derives from the heart, and by virtue of which they dilate and contract. Put together, therefore, the two facts--that the arteries have this motion, and that everything, when it dilates, draws neighbouring matter into itself--and you will find nothing strange in the fact that those arteries which reach the skin draw in the outer air when they dilate, while those which anastomose at any point with the veins attract the thinnest and most vaporous part of the blood which these contain, and as for those arteries which are near the heart, it is on the heart itself that they exert their traction. For, by virtue of the tendency by which a vacuum becomes refilled, the lightest and thinnest part obeys the tendency before that which is heavier and thicker. Now the lightest and thinnest of anything in the body is firstly pneuma, secondly vapour, and in the third place that part of the blood which has been accurately elaborated and refined.