2. But inasmuch as the blood and the veins seem to occupy the chief place, we will first of all speak of these, both for other reasons, and because former writers do not appear to have described them rightly. The difficulty of understanding them is the reason of their errors, for in dead animals, the nature of the principal veins is obscure, for they collapse as soon as the blood has escaped, and it pours out of them as from a vessel. No part of the body, except the veins, contains any blood, except the heart, which has a little; but it is all in the veins. In living creatures their nature cannot be distinguished, for they are internal, and out of sight; so that those who consider them only in dead and dissected animals, cannot see their principal origins. But some, by the examination of emaciated persons, have distinguished the origin of the veins, from the appearance of those which are external. 3. For Syennesis,[89] a Cyprian physician, speaks thus: "The larger veins are thus constituted. From the navel around the loins, through the back to the lungs, under the breasts; that from the right to the left, and that from the left to the right. That from the left, through the liver to the kidney and the testicle; that from the right to the spleen, the kidney, and the testicle, and from thence to the penis." [89] Syennesis, a physician of Cyprus. Very little is known of him; he must have lived in or before the fourth century B.C. 4. Diogenes[90] of Apollonia writes thus: "The veins are thus placed in man. There are two very large ones, which extend through the stomach by the spine of the back, one to the right and the other to the left, each to the leg nearest itself, and upwards to the head by the collar-bone, and through the neck. From these great veins others extend through the whole of the body, from the right to the right side, and from the left to the left side. The largest are two from the heart, surrounding the spine of the back; and others, a little higher up, through the breasts under the arm-pits, each to the hand nearest itself; and the one is called the splenetic, the other the hepatic vein. [90] Diogenes of Apollonia was an eminent natural philosopher of Crete, in the fifth century B.C. He wrote a work, περὶ φύσεως, in which he treated of natural philosophy in the widest sense of the words: a few fragments are still extant, of which this quoted by Aristotle is the longest.