The alligator and its allies

by A. M. Reese

Just distal to the thoracic the axillary vein receives two fairly large vessels, the subscapulars, sc, that return blood from the shoulder and upper arm. After receiving the subscapulars, the axillary may be followed into the upper arm as the brachial, br. As has been said, the brachial and postbrachial anastomose near the elbow, and in this region the former receives a small vessel that extends parallel to it from the manus.

In the forearm the brachial may be called the radial, [Fig. 60], A, ra; on the back of the manus the radial receives branches from the various digits and from a rather complex plexus of vessels in the carpal region.

The external jugular, [Fig. 60], ej, after separating from the subclavian, may be traced cephalad, close beneath the skin, to the base of the skull, where it is connected with the internal jugular by short branches, as has already been noted. It receives several small branches from the skin and muscles of the neck and shoulder regions. At the region of its anastomosis with the internal jugular it receives a large branch, the muscular, ms, from the massive muscle at the angle of the jaw and from the skin of that region.

A short distance cephalad to the muscular the external jugular receives, on its mesial side, two or three branches from the trachea, larynx, and œsophagus, tr. Anterior to these vessels the external jugular is formed by the union of two chief veins, the lingual, l, from the ventro-lateral surface of the tongue, and the inferior dental, id, from the mesial surface of the lower jaw. The connection of the superior dental (extending along the bases of the maxillary teeth) with the jugular could not be determined with certainty, hence that vessel is not shown in the figure. The same is true of the small veins in the region of the cranium.

The Arterial System

The Abdominal Aorta and its Branches.

The right and left aortic arches, [Fig. 61], Aod, Aos, arising from the heart in the manner already described, form a rather long loop and approach each other in the middorsal line. Here they are united by a short, wide connective in such a way that the left arch seems continued into the cœliac artery and the right into the dorsal aorta proper. Each arch, anterior to the connective, gives off two fairly large branches, oe, to the posterior region of the œsophagus.

The cœliac artery, [Fig. 61], c, is the largest branch of the abdominal aortic system. After giving off a couple of small branches, oe, to the posterior region of the œsophagus, it gives off a large spleno-intestinal artery, si, to the spleen and small intestine.

The cœliac then breaks up into three arteries of about the same size: the gastro-hepatico-intestinal, ghi, carrying blood to the stomach, liver, and small intestine; the pancreo-intestinal, pi, leading to the pancreas and small intestine; and the gastric, ga, to the greater part of the stomach.

From the dorsal aorta proper, da, which, as has been said, seems to be the direct continuation of the right aortic arch, several arteries are given off; these will be described as they occur in an antero-posterior direction.