Section 45. the Following Are the Chief Branches of the Aorta. the

student should be able to follow them with certainty in dissection; they are all displayed in the Figure; but it must not be imagined for a moment that familiarity with this diagram will obviate the necessity for the practical work; (in.) is the innominate artery; it forks into (s.cl.a.) the right subclavian, and (r.c.c.) the right common carotid. Each carotid splits at the angle of the jaw into an internal and an external branch. The left common carotid, (l.c.c.) arises from the base of the innominate,* (l.s.cl.a.) the left subclavian, directly from the aorta. The aorta now curves round to the dorsal middle line, and runs down as seen in Figure 1, Sheet 1 (d.ao.) and Figure 1, Sheet 2 (d.ao.). Small branches are given off to the ribs, and then comes the median coeliac (coe.a.) to the stomach and spleen, the median superior mesenteric (s.mes.a.) to the main portion of the intestine, and the inferior mesenteric (p.m.a.) to the rectum. Note that no veins to the inferior vena cava correspond to these arteries-- the blood they supply going back by the portal vein (p.v.). The paired renal arteries (r.a.) supply the kidneys, and the common iliacs (c.il.a.) the hind legs, splitting into the internal iliacs (i.il.a.) and the femoral (f.).

{Lines from Second Edition only.} [The student should note that the only arteries in the middle line are those supplying the alimentary canal.]

{Lines from First Edition only.} * -The figure is inaccurate, and represents the left common carotid as arising from the aortic arch.-