THE HEART. 275 
a single pulmonary artery (Fig. 115, 7). It returns to the 
left auricle by the numerous pulmonary veins (Fig. 116, g, 
h, 7), 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 (9), 
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 (4) ventricles. The apex thus 
belongs to the left ventricle. From the cranial end of the 
right ventricle the pulmonary artery (f) 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 (@) is larger and bent at right angles, so that its free end 
is directed toward the apex. 
In the dorsal view (Fig. 116) 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 (4) with the pulmonary veins (g, 2, 2) 
opening into it. Craniad of the right ventricle (@) is the right 
auricle (c) with the vene cave (d and ¢) opening into it near 
the middle. Coming from beneath the auricles are seen the 
pulmonary artery (7) and the aorta (/). 
The chambers of the heart. 
1. The right auricle (atrium dextrum) (Figs. 115 and 
116, c). Externally the right end of the right auricle projects 
so as to form its auricular appendage (Fig. 115, ¢) which lies 
at the right of the base of the aorta (Fig. 115, g). The 
superior vena cava (Fig. 116, ¢) is seen entering near the 
cranial end of the auricular septum opposite the base of the 
aorta. The inferior vena cava (Fig. 116, @) enters the auricle 
near the coronary sinus and close to the auricular septum. 
The netted appearance which the wall, especially that of the 
