The Postcardinal Veins. (Plates 44 and 45.)

Each postcardinal vein is a moderately stout vessel which, at its posterior extremity, is united either with the postcaval vein itself or with one of the main efferent renal veins which form the postcaval vein. From this posterior point of union, each postcardinal curves slightly outward to reach the corresponding kidney, and is closely applied to the inner edge of the anterior third of that organ. This condition is undoubtedly correlated with the fact that the relative length of the kidneys in Leiopelma is rivalled among Amphibia only by that found in Ascaphus and the caecilians.

From the anterior extremity of the kidney, the postcardinal vein passes forward almost to the level of the arm, lying in close proximity to the lateral edge of the systemic arch. A short distance behind the level of the subclavian artery, the postcardinal vein curves outward towards the arm, the exact degree and position of the curvature varying with the individual. After passing forward for a short distance, the vein turns inward again and passes across to the heart, forming by its union with the main veins from the anterior region of the body, a wide channel, the ductus Cuvieri, opening into the lateral aspect of the sinus venosus.

The postcardinal vein receives a number of tributaries, some of which are of major importance, while others are merely small vessels draining muscles.