THE HEART. 275 



a single pulmonary artery (Fig. 1 1 5 , /). It returns to the 

 left auricle by the numerous pulmonary veins (Fig. 116, g, 

 h, /), and passes thence to the left ventricle. From the left 

 ventricle it passes to the body by a single aorta (Fig. 115, g]. 



When the heart is viewed from the ventral surface (Fig. 

 115), a considerable blood-vessel, the coronary artery (q), 

 running from the base to a point a little to the right of the 

 apex, indicates the position of the septum (ventricular septum), 

 between the right (a) and left (b} ventricles. The apex thus 

 belongs to the left ventricle. From the cranial end of the 

 right ventricle the pulmonary artery (/") is seen passing 

 obliquely craniad and toward the left. Beneath the pulmonary 

 artery the aorta (g) appears rising from the middle of the base 

 of the heart and passing directly craniad. At the base appears 

 a part of the auricular appendage of the left auricle (*/), and at 

 the right a part of the right auricular appendage (c). The 

 former (d) is larger and bent at right angles, so that its free end 

 is directed toward the apex. 



In the dorsal view (Fig. 1 16) the position of the ventricular 

 septum is not indicated. On the surface of the left ventricle a 

 short distance from the ventricular septum and nearly parallel 

 to it are seen branches of the coronary artery and the coronary 

 vein passing toward the apex. Craniad of the left ventricle is 

 seen the left auricle (b] with the pulmonary veins (g, //, z) 

 opening into it. Craniad of the right ventricle (a) is the right 

 auricle (c) with the venae cavae (d and e] opening into it near 

 the middle. Coming from beneath the auricles are seen the 

 pulmonary artery (j) and the aorta (/). 



The chambers of the heart. 



i . The right auricle (atrium dextrum) (Figs. 1 1 5 and 

 116, c}. Externally the right end of the right auricle projects 

 so as to form its auricular appendage (Fig. 115, c] which lies 

 at the right of the base of the aorta (Fig. 115, g}. The 

 superior vena cava (Fig. 116, e] is seen entering near the 

 cranial end of the auricular septum opposite the base of the 

 aorta. The inferior vena cava (Fig. 116, d} enters the auricle 

 near the coronary sinus and close to the auricular septum. 

 The netted appearance which the wall, especially that of the 



