Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/113

Rh Carefully clear away the tissues in which the inferior vena cava is imbedded and find the lumbar veins, which join the dorsal side of the inferior vena cava. Note their number, position, and distribution.

Exercise XXV. Make a full-page drawing of the veins anterior and posterior to the heart, incorporating the sketch required by Exercise XIV.

The descending aorta is the posterior continuation of the aortic arch. It courses caudally through the thorax and abdomen, ventral to the vertebral column, carrying blood to the body walls, viscera, hind limbs, etc. Its position and conspicuous size make its identification easy. The main branches are as follows, beginning at the anterior end of the series.

The paired intercostal arteries pass dorsally from the thoracic section of the aorta to the muscles between the ribs. Determine the number, arrangement, and distribution of these arteries.

The first large artery leaving the dorsal aorta after it enters the abdominal cavity is the coeliac. Passing ventrally, this divides into three branches: the splenic, the hepatic, and left gastric arteries. The splenic artery splits into several branches which terminate in the spleen. It sends smaller rami to the pancreas and stomach. The hepatic artery, some distance from its origin, delivers blood to the following branches. The right gastric artery goes to the region of the pylorus, thence along the lesser curvature of the stomach, and anastomoses with the left gastric artery, which is described below. The right gastro-epiploic artery passes to the greater curvature of the stomach. The superior pancreatico-duodenal artery courses along the