I n connection with the preceding study of the lymphatic system it was necessary to reconstruct the veins of the shoulder and hip in a series of rabbit embryos. The reconstructions were then extended to include the distal portions of these vessels, complete figures of which had never been published. Hochstetter, in 1891, had observed the veins in the limbs of living rabbit embryos, and had studied them in serial sections. His drawings, however, show only detached portions of the veins such as could be seen under most favorable conditions, in living embryos. Ten years later Grosser described but did not reconstruct, the developing veins in the extremities of bats. To these two investigators embryology is indebted for the present knowledge of the veins in mammalian limbs. It is proposed to review their work, while describing t,he reconstructions, considering first the veins of the anterior extremity, then those of the posterior extremity, and finally the homologies which exist between the two sets.
VEINS OF THE ANTERIOR EXTREMITY. I n the youngest rabbit figured, an embryo of 13 days, Fig. , p. 9'7, the small vessels along the radial or anterior border of the arm unite to form a vein which follows the periphery of the limb to its posterior or ulnar border, and then ascends behind the brachial plexus to terminate near the junction of the anterior and posterior cardinal veins. It receives a branch which at this stage is not well defined, ascending in the body wall. This is the Seitenrmmpfvene of Hochstetter, and becomes the external mammary vein of the adult.
According to Hochstetter, in rabbits of 12 and 12% days, the " border vein" makes a complete circuit of the limb, and its radial part either empties into the ulnar vein near its termination or connects with the cardinal vein directly. But this radial vein is said to be hard to follow