Chapter IV.

1. The veins, then, are thus distributed in the parts above the heart, but the part of the great vein which is below the heart passes through the middle of the diaphragm, and is united to the aorta and spinal column by membranous flaccid passages. From this a short and wide vein passes through the liver, from which many similar branches extend to the liver, and disappear upon it. There are two branches of the vein, one of which terminates upon the diaphragm, and what is called the præcordia, the other returns through the arm-pit to the right arm, and unites with the other veins near the interior part of the elbow. For this reason physicians treat certain diseases of the liver by venesection in this vein.

2. From the left of this there is a short and wide vein, which reaches to the spleen, and the branches of this vein are lost upon this organ, and another portion branching off in the same way from the left the great vein passes up to the left arm, except that the last-mentioned pass through the liver, but this one through the spleen. Other branches also separate from the great vein, the one to the omentum, the other to the pancreas; and from this many veins extend through the mesenterium, and all end there in one great vein, which passes through the whole intestine and the stomach, as far as the œsophagus; and many veins branch off from them around these parts.

3. Both the aorta and the great vein continue as far as the kidney each as a single duct; from this point they are more closely united to the spinal column, and are each divided into two parts, like the letter lambda (Λ), and the great vein is placed farther back than the aorta. The aorta is more closely united to the spinal column, near the heart, and the junction is formed by small sinewy veins.

4. The aorta leaves the heart as a large hollow passage, but as it advances it becomes narrower and more sinewy. From the aorta, veins extend also to the mesenterium, like those from the great vein, but far inferior in size, for they are narrow and muscular. They terminate in small hollow muscular veins. No branch of the aorta extends to the liver and the spleen, but the branches of either vein extend to each hip, and both touch upon the bone. Branches reach the kidney both from the great vein and the aorta; they do not, however, enter the cavity, but are taken up in the substance of the kidney.

5. Two other strong and continuous passages reach from the aorta to the bladder, and others from the cavity of the kidney; but these do not communicate with the great vein. From the centre of each kidney a hollow sinewy vein passes through the other veins to the spinal column; first of all they disappear upon each hip, and then appear again in branches towards the hip; their extremities are distributed upon the bladder and penis in the male, and upon the uterus in the female; no branch of the great vein passes to the uterus, but many and thick ones reach it from the aorta.

6. From the aorta and great vein branches are distributed to the nates; at first they are large and hollow, afterwards they pass through the legs, ending upon the feet and toes; and others again pass through the nates and thighs, alternately from right to left, and they join with other veins below the knees.

7. The nature and origin of the veins are evident from this description. In all sanguineous animals, the nature and origin of the principal veins are the same, but the multitude of smaller veins is not alike in all, for neither are the parts of the same nature, nor do all possess the same parts. Nor are the veins equally apparent in all animals; but they are more manifest in those which have most blood, and in the largest creatures; but in those animals which are small, and have not much blood, either by nature or from excess in fat, they are not so easily investigated, for some of the passages are confused, like rivulets that are lost in beds of mud; and there are some animals which have but few, and these fibres instead of veins. The great vein is very conspicuous in all, even the smallest animals.