236 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



into the muscles attached to the scapula. A little farther posteriorly the vessel 

 forks into the first intercostal artery which runs laterally along the carapace and 

 then turns posteriorly in the curve of the carapace, and the vertebral artery which 

 passes dorsal to the first rib and runs posteriorly in this position accompanying 

 the vertebral vein. In its course it gives rise at the sutures of the costal plates 

 to the intercostal arteries which join the communicating margino-costal artery 

 situated in the curve of the carapace, alongside the vein of the same name. 



Each carotid artery passes forward along the ventral side of the neck, soon 

 crossing dorsal to the subclavian and then coming to lie medial to the subclavian. 

 In specimens in which the neck is drawn into the shell the carotids usually make 

 loops in the neck region. As the carotid artery passes the thymus gland it gives 

 branches into the gland. It then proceeds, without branching, the entire length 

 of the neck in contact with the internal jugular vein and the vagus nerve, and 

 enters the skull by a foramen in front of the auditory region. 



Draw the brachiocephalic artery and its branches. 



b) The pulmonary arteries: The pulmonary artery is the one farthest to the 

 left of the three arterial trunks which spring from the ventricle. It divides 

 immediately into right and left pulmonary arteries. To see this division lift the 

 pulmonary trunk and look on its dorsal side. Trace the left pulmonary first. It 

 proceeds laterally posterior to the left aorta to which it is more or less bound 

 by connective tissue, forming the arterial ligament or ligament of Botallus. (The 

 significance of this ligament will be explained later.) The pulmonary proceeds 

 directly to the left lung in company with the left bronchus and left pulmonary 

 vein. Trace the right pulmonary in the same way. It is bound to the right 

 aorta by the right arterial ligament. 



Add these to the preceding drawing. 



c) The right and left aortae: Trace both of these arteries away from the heart. 

 Each makes & curve as it leaves the heart and turns posteriorly, passing dorsal 

 to the precaval vein, the bronchi, and the pulmonary vessels, and disappearing 

 dorsal to the lobes of the liver. Vessels already studied may be cut to follow 

 the aortae posteriorly. Trace the left aorta first. Grasp the stomach and left 

 lobe of the liver and press them to the right, separating the cardiac end of the 

 stomach from the lung. The left aorta will be found passing to the left of the 

 esophagus and dorsal to the stomach. It gives off simultaneously three large 

 branches. One of these is the gastric artery which passes to the stomach in the 

 cardiac region and follows the curve of the stomach along the length of this organ. 

 After a short distance it forks into anterior and posterior gastric arteries which 

 supply the lesser and greater curvatures of the stomach respectively. Another 

 branch from the dorsal aorta is the coeliac artery. It soon forks into anterior 

 and posterior pancreatico-duodenal arteries. The anterior pancreatico-duodenal 

 artery passes to the left end of the pancreas, gives off there branches into the 

 pyloric end of the stomach and to the liver, then turns to the right and runs 



