3. All these are perforated towards the lungs, but imperceptibly so from the minuteness of the passage, except in one place. The great vein is suspended from the upper portion of the principal cavity, and on the right side; afterwards through the cavity a vein extends again, as if the vein were a part of the cavity in which the blood stagnates. The aorta has its origin from the middle cavity, but in a different manner from the vein, for it communicates with the heart by a much narrower passage, and the vein is continued through the heart. But the aorta passes from the heart, and the great vein is membranous and like skin, but the aorta is narrow and very sinewy, and as it is continued towards the head and the lower parts of the body, it becomes narrow and quite sinewy. 4. A portion of the great vein is first of all extended upwards from the heart to the lung, and to the junction of the aorta, this vein being undivided and large; from this place it divides into two branches, the one towards the lung, and the other to the spine and the lowest vertebra of the neck. The branch which goes to the lungs is first divided into two branches, and afterwards it is continued upon every tube and passage of the lungs, greater to the greater, and less to the less, so as to leave no part in which there is not a passage and a small vein. These last are invisible from their minute size, so that the whole lung seems to be full of blood. 5. And the passages from the vein are above the tubes which extend from the trachea. And the vein which is continued upon the vertebra of the neck, and upon the spinal column, returns again to the spine, as Homer writes in his poems: "He cut off the whole vein which passes up the back and returns again to the neck;"[92] and from this vein branches extend to each rib and to each vertebra; but that which is upon the vertebra near the kidneys branches in two directions. These branches, then, of the great vein are subdivided in this manner. [92] Iliad. xiii. 546. 6. And above these, from that part which is continued from the heart, the whole is again divided into two directions, for some reach to the sides and the clavicles, and afterwards through the armpits to the arms, in the human subject, but in quadrupeds to the fore-legs, to the wings in birds, and to the pectoral fins in fishes. The commencements of these veins, when they are first of all divided, are called jugular veins; and having branched off in the neck from the great vein, they are continued to the trachea of the lungs. And if these veins are held on the outside, men fall down dead with insensibility, with closed eyes, but without choking.