26o Anatomy of the Rabbit. 



(a) The posterior, somewhat conical, ventricular portion of the 

 heart. The left ventricle (ventriculus sinister) may be dis- 

 tinguished both by its position and by the more solid charac- 

 ter of its wall. The right ventricle (ventriculus dexter) is 

 less muscular, and the wall is readily pressed inward. The 

 line of division is indicated on the ventral surface by a faint 

 depression, the anterior longitudinal sulcus. 



(b) The pulmonary artery (a. pulmonalis) leaves the base of 

 the right ventricle, passing forward and to the left in a some- 

 what spiral fashion around the aorta. On the dorsal sur- 

 face of the latter it divides into the right and left pulmon- 

 ary arteries , one for each lung. At the point of division the 

 pulmonary artery is connected with the aorta by a short 

 fibrous cord, the arterial ligament (lig. arteriosum), repre- 

 senting the foetal connection of the two vessels through the 

 ductus arteriosus (p. 89). 



(c) The left coronary artery (a.'coronaria sinistra) passes back- 

 ward on the ventral surface of the heart, lying in the anterior 

 longitudinal sulcus. A corresponding right coronary 

 artery (a. coronaria dextra) passes to the right side of the 

 heart, lying between the right ventricle and the right 

 atrium. 



The two vessels supply the substance of the heart. They are the 

 first branches of the aorta, arising from the aortic sinuses at its base. 



(d) The left atrium (atrium sinistrum) is the thin-walled 

 chamber lying to the left at the base of the heart. The 

 pulmonary veins (venae pulmonales), several on either 

 side, enter the left atrium, passing from the medial portions 

 of the lungs. 



(e) The right atrium (atrium dextrum) resembles the left in 

 the character of its wall. It receives the right and left 

 superior caval veins and the unpaired inferior caval vein. 



The heart may be removed by dividing the great bloodvessels. 

 The arch of the aorta should be removed with the heart by dividing 

 the vessel at a point beyond the origin of the left subclavian, and 

 then severing the carotids and subclavians at their bases. This 

 exposes the surface for the subsequent examination of the posterior 

 end of the trachea and its connections with the lungs. 



