178 ANATOMY AND PHYSIOLOGY 



The interior of the ventricles is marked with a number of ridges 

 or bands of muscle fibers (the trabeculce carnece), and certain of 

 these are attached by tendinous cords to the valves of the heart. 

 Each ventricle opens into a large artery, which conveys the blood 

 away the pulmonary artery from the right ventricle, the aorta 

 from the left. 



3" 



FIG. 120. INTERIOR or LEFT HEART. (Observe the difference in thickness of 



the walls in auricle and ventricle.) (Allen Thomson in Brubaker.) 

 i, L. atrium or auricle; 2, division between it and ventricle; 3, wall of left ventricle; 

 4,_a band of muscle fibers severed; 5, other muscle bands; 6, a leaflet of mitral valve, 

 with tendinous cords; 7, aorta (a large artery) laid open to show semilunar valves; 8, 

 pulmonary artery (semilunar valves closed) ; 9, arch of aorta. 



Note. In the new nomenclature the name "atrium," or forechamber , is 

 given to the main part of the auricle, and the word auricle applies to the 

 auricular appendage alone. 



Endocardium. The lining of the heart. It is thin and firm, 

 resembling serous membrane in appearance, and is continuous 

 with the lining of the blood-vessels, thus making a perfectly 



