VISCERA 23 



much thicker walls than those of the auricle. It 

 receives the blood from the right auricle and 

 pumps it out at its anterior end through the pul- 

 monary artery. The opening of this artery is 

 guarded by three flaps, the semilunar valves. 



c. The Left Auricle lies on the anterior dorsal 

 side of the heart. It receives at its dorsal end the 

 pulmonary veins, usually two on each side. The 

 left auricle opens into the left ventricle through 

 an aperture guarded by a valve similar to the tri- 

 cuspid but with only two flaps, the mitral valve. 



d. The Left Ventricle is by far the most muscular 

 portion of the heart. It occupies nearly the whole 

 posterior portion of the organ. Its cavity is oval 

 and receives the blood from the left auricle and 

 forces it out through the aorta, whose opening is 

 guarded by semilunar valves similar to those of 

 the pulmonary artery. 



The two coronary arteries which convey blood 

 to the heart itself lead from the aorta just outside 

 of the semilunar valves. 



VISCERA OF THE HEAD AND NECK. 



Remove the skin from the head and neck. 

 A. — Salivary Glands. 



I. The Parotid Gland, the largest of the salivary 

 glands, lies just beneath the skin at the ventral 

 margin of the cartilage of the ear. Its duct, 

 Stensons duct, may be seen as a fine white canal 



