274 THE RABBIT 



(b) The anterior mesenteric, formed by veins. from the ileum and 



large intestine. 



(c) The duodenal, from the duodenum and pancreas. This vein 



lies under the pancreas in the mesentery which joins the two 

 limbs of the duodenum. 



(d) The lieno-gastric, formed by the union of smaller veins from the 



stomach and spleen. 



(ii) The canal is supplied by the following arteries arising from the dorsal 

 aorta : — 



(a) The eoeliae, branching into an hepatic to the liver and a lieno- 



gastric to the stomach and spleen. 



(b) The anterior mesenteric, supplying the duodenum and pancreas, 



the ileum, the caecum, and the colon. 



(c) The posterior mesenteric, to the posterior portion of the rectum. 



Make a complete sketch showing the alimentary canal with the blood-vessels 

 supplying it. {See Fig. 92, p. 276.) 



The Structures of the Neck. 



Make a careful dissection of the neck region so as to expose the following 

 parts : — 



A. The Trachea or windpipe, extending along the middle line of the neck 



and concealing most of the oesophagus. It has rings of cartilage in its 

 walls and they are incomplete dorsally. {See Trachea, page 268.) 



B. The Larynx, the organ of voice, is the anterior part of the trachea. 



Externally may be noted the large anterior thyroid cartilage and 

 the smaller posterior ring-like cricoid cartilage, which form the outer 

 wall of the larynx. 



C. The Thyroid, a two-lobed body, one lobe lying on either side of the 



cricoid cartilage of the larynx. The lobes are connected by a ventral 

 isthmus. 



.D. The Nerves. 



(a) The cervical sympathetic cords, arising in the head and passing back- 

 wards one on either side of the trachea between the vagus and 

 depressor nerves. Anteriorly in the neck region each has two ganglia, 

 the superior cervical sympathetic and the inferior cervical sympathetic 

 ganglion. In the thorax each cord has twelve ganglia, and in the 

 abdomen there are also twelve. 

 {b) The vagus or pneumogastric nerves are the tenth cranial nerves, and 

 each emerges just at the posterior end -of the mandible. Here it gives 

 rise to the vagus ganglion and then branches to form : 



(i) The vagus nerve, a stout cord running parallel to the trachea, 

 along the outer side of the carotid artery, and supplying the 

 heart, lungs, oesophagus and stomach, 

 (ii) The superior laryngeal nerve, which nms from the ganglion 

 straight across the trachea to the thyroid cartilage. 



