| OCR Text |
Show 1904.] CIRCULATORY SYSTEM IX THE OPHIDIA. 347 the eighth intercostal and again on the right side. The common trunk formed does not enter the liver directly, but joins the portal vein. This is also the case with the last of this series of portals, which arises, also to the right of the median line, just behind the ninth intercostal. The following parietal portals are connected with the suprarenal bodies. In the second and male individual there are some differences in the arteries and veins in question. There are two intercostals in front of the junction of the aorta and twelve between this point and the origin of the superior mesenteric. All the arteries, however, are exactly median in position where they perforate the body-wall. There are nine or ten portals arising from the left side which extend down to a point about opposite to the end of the liver. I cannot give an accurate description of how some of them join each other before entering the liver. After these, six trunks arise on the right side, each three forming a single trunk. The last of these vessels joins the portal vein before it reaches the liver. From the origin of the superior mesenteric artery to the cloacal aperture there are 16 vertebral arteries, all of which, as before, perforate the body-wrall in the dorsal median line. The arrangement of these is peculiar, in that they alternate in their points of origin from the dorsal aorta. This obviously suggests an originally paired series which have been pulled asunder in an antero-posterior direction by the lengthening of the body. Oesophageal Branches.-The oesophageal branches are all very slender and fairly numerous. The section of oesophagus which lies in the fork formed by the right and left aorta is supplied from three distinct sources. There is, first of all, a slender artery which emerges from the body-wall in company with a vein to the right of the middle line. Anteriorly there are one or two similar arteries which may emerge from the middle line. The chief blood-supply, however, of this part of the oesophagus is from two vessels arising from the right aorta, between which arises a third branch supplying part of the oesophagus behind the junction of the aorta?. The left aorta provides two branches, one arising near its commencement, and another wThich is very inconspicuous and given off not far from the junction with the right aorta. After the junction of the aorta? and before the beginning of the liver I counted four oesophageal arteries. In the region of the liver the same arteries supply both liver and oesophagus or stomach as the case may be. There are 8 of these arteries, which increase in length and strength towards the stomach. These 8 arteries are followed by ofie which serves the stomach and the gall-bladder, spleen, and pancreas onty. It is the single gastric artery, and indeed it practically supplies the stomach only, the twig to the other viscera being excessively minute; these viscera are, in fact, cared for by the superior mesenteric. This vessel, as usual, has two main branches-an intestinal and a gastro-splenic. But before its division into these |
