i 
= 
THE HEART. 739 
neighbouring structures, the heart lies in the middle mediastinum, and rests below 
on the diaphragm. Its long axis, from base to apex, runs obliquely from behind 
forwards, downwards, and to the left. 
The base (basis cordis), formed entirely by the auricles, and almost entirely by 
the left auricle, is directed upwards, backwards, and to the right. It les in front 
of the descending thoracic aorta, the cesophagus, and the lower right pulmonary 
vein, which separate it from the bodies of the fifth, sixth, seventh, and eighth 
dorsal vertebree. ; 
On the whole the base is somewhat flattened, and it is irrecularly quadrilateral 
in form. It presents the orifices of the superior and inferior vene cave and the four 
pulmonary veins.. The opening of the superior vena cava is situated at the upper 
right angle, that of the inferior cava occupies the lower angle on the right side; 
Ligamentum arteriosum Aorta 
Right pulmonary artery 
: EnSy CHEE : ‘ 
Left pulmonary artery. wy Superior vena cava 
Vestigial fold__} 
of Marshall F = , : IN Right pulmonary veins 
Z | | 
i 
Left pulmonary veins<_ = 
Sulcus terminalis 
Oblique vein 
of Marshall 
Transverse branch of 
left coronary artery 
— Inferior vena cava 
Left marginal artery 
right ventricle 
Left ventricle 
Coronary sinus 
Fic, 545.—THE Bask AND INFERIOR SURFACE OF THE HEART, showing the openings of the great vessels 
and the line of reflection of the serous pericardium. 
between these are the orifices of the two right pulmonary veins, and immediately 
to the right of the latter is the indistinct posterior interauricular sulcus, which 
descends to the left of the orifice of the inferior vena cava. The openings of the 
two left pulmonary veins are situated near the left border of the base; and the 
portion of the surface which lies between the right and left pulmonary veins 
forms the anterior boundary of the great oblique sinus of the pericardium. 
The base is limited below by the lower part of the auriculo-ventricular groove, 
in which the coronary sinus lies; its upper border is in relation with the bifur- 
cation of the pulmonary artery. <A fold of pericardium, the vestigial fold of 
Marshall (ligamentum v. cavee sinistree) descends, near the left border of the base, 
from the left branch of the pulmonary artery above to the left superior pulmonary 
vein below; and from the lower end of this fold, crossing obliquely below the left 
pulmonary vein to reach the coronary sinus, is the small oblique vein of Marshall 
(v. obliqua atrii sinistri [Marshalli]). Further, it is from the base that the 
visceral layer of the pericardium which elsewhere completely invests the heart 
