Chapter III.

1. The opinions of other persons are nearly these; and there are other physiologists, but they have not treated so accurately of the veins. But all agree in placing their origin in the head and brain, in which they are incorrect. But, as I have remarked before, it is difficult to discern the course of the veins; indeed, it is impossible to understand them unless a person will examine animals which, after emaciation, have been killed by strangulation. The following is the nature of the veins: There are two veins in the interior of the chest, near the spine; the larger of these is placed forward, the smaller is behind; the larger is inclined to the right side, the smaller to the left; and this by some persons is called the aorta, from the sinewy portion which is seen in dead animals.

2. These veins have their origin in the heart, for they pass completely through the other intestines, and always preserve the character of veins. The heart is, as it were, a part of them, and especially of the more forward and larger one, for these veins are above and below, and the heart is in the middle of them. The heart of all animals contains cavities, but in the heart of very small animals the largest cavity is scarcely perceptible, in moderately sized animals the second cavity is scarcely visible, but in large animals they are all three distinct enough. And when the apex of the heart is turned forwards, as I have observed, the principal cavity is on the right side, and above it the least is on the left side, and the middle-sized one is between them; the two smaller are far less than the greater.

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.

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.

7. Extending in this manner, and receiving the trachea between them, they reach the place where the jaws unite with the head; and again from this point they are divided into four veins, one of which bends backwards and descends through the neck and shoulder, and meets the first division of the vein by the joint of the arm; the other portion terminates in the hand and fingers; and another branch extends from each part near the ear to the brain, where it is divided into many small branches upon the membrane which surrounds the brain.

8. The brain never contains blood in any animal, nor does any vein, small or great, terminate upon it; but some of the other branches that extend from this vein surround the brain in a circle, and others, end upon the organs of sense and the teeth in very small veins. In the same manner, also, the branches of the smaller vein, which is called the aorta, are divided: they are continued beside those of the great vein, but the tubes are smaller and the branches less than those of the great vein.