Page:1888 Cicero's Tusculan Disputations.djvu/314

 ; they alternately dilate and contract to receive and return the air, that what is the chief animal sustenance may be always fresh. The juice, by which we are nourished, being separated from the rest of the food, passes the stomach and intestines to the liver, through open and direct passages, which lead from the mesentery to the gates of the liver (for so they call those vessels at the entrance of it). There are other passages from thence, through which the food has its course when it has passed the liver. When the bile, and those humors which proceed from the kidneys, are separated from the food, the remaining part turns to blood, and flows to those vessels at the entrance of the liver to which all the passages adjoin. The chyle, being conveyed from this place through them into the vessel called the hollow vein, is mixed together, and, being already digested and distilled, passes into the heart; and from the heart it is communicated through a great number of veins to every part of the body. It is not difficult to describe how the gross remains are detruded by the motion of the intestines, which contract and dilate; but that must be declined, as too indelicate for discourse. Let us rather explain that other wonder of nature, the air, which is drawn into the lungs, receives heat both by that already in and by the coagitation of the lungs; one part is turned back by respiration, and the other is received into a place called the ventricle of the heart. There is another ventricle like it annexed to the heart, into which the blood flows from the liver through the hollow vein. Thus by one ventricle the blood is diffused to the extremities through the veins, and by the other the breath is communicated through the arteries; and there are such numbers of both dispersed through the whole body that they manifest a divine art. Why need I speak of the bones, those supports of the body, whose joints are so wonderfully contrived for stability, and to render the limbs complete with regard to motion and to every action of the body? Or need I mention