THE BLOOD-VASCULAR SYSTEM OF THE OX 705 
ried into the right atrium by the posterior vena cava passes largely, if not entirely, 
through the foramen ovale into the left atrium, while the blood flowing into it 
through the anterior vena cava passes into the right ventricle. On this basis the 
blood received by the left atrium consists chiefly of mixed blood from the posterior 
vena cava, since the small amount of blood conveyed by the pulmonary veins is 
yenous. This mixed blood passes into the left ventricle and is forced into the 
systemic arteries. The venous blood from the anterior part of the body and the 
thoracic limbs is conveyed by the anterior vena cava to the right atrium, passes 
into the right ventricle, and is forced into the pulmonary artery. A small amount 
is carried to the lungs, but the bulk of it passes by the ductus arteriosus into the 
aorta behind the point of origin of the brachiocephalic trunk, and is carried to the 
posterior part of the body, a large part passing by the umbilical arteries to the 
placenta. 
THE BLOOD-VASCULAR SYSTEM OF THE OX 
THE PERICARDIUM AND HEART 
The pericardium is attached to the sternum opposite the facets for the sixth 
costal cartilages by two fibrous bands, the sterno-pericardiac ligaments (Ligg. 
sternopericardiaca) ; these ligaments, right and left, are embedded in the mass of fat 
which separates the apex of the pericardium from the floor of the thorax. On the 
left side the greater part of the pericardium is in contact with the chest wall as far 
back as the fourth intercostal space. On the right side the pericardium is com- 
monly covered by the lung, and has therefore no contact with the lateral chest wall. 
But in some cases there is a small cardiac notch on the right lung opposite to the 
ventral part of the third rib and intercostal space. 
The heart of the adult ox has an average weight of about five and a half pounds 
(ca. 2.5 kg.), or about 0.4 to 0.5 per cent. of the body-weight. Its length from base 
to apex is relatively longer than that of the horse, and the base is smaller in both 
its diameters. The ventricular part is more regularly conical and more pointed. 
A shallow intermediate groove (Sulcus intermedius) extends from the coronary 
groove down the left side of the posterior border, but does not reach the apex. The 
amount of fat in and near the grooves is much greater than in the horse. Even 
more of the heart is situated to the left of the median plane than in the horse. The 
base is opposite the chest wall from the third rib to the fifth intercostal space, both 
inclusive. The apex is opposite to the fifth interchondral space; it is just to the 
left of the median plane, and is about an inch (ca. 2.5 em.) from the diaphragm. 
The long axis is much less oblique than in the horse. The posterior border is 
opposite to the fifth intercostal space; it is practically vertical and is slightly con- 
cave. 
The pulmonary orifice is opposite to the third rib in part and the third intercostal space, 
about a handbreadth (ca. 10-12 em.) above the sternal ends of the ribs. The aortic orifice is 
chiefly opposite to the fourth rib. The right atrio-ventricular orifice is opposite to the third inter- 
costal space and fourth rib and space. The left atrio-ventricular orifice is chiefly opposite to the 
fourth intercostal space and fifth rib. 
_ The left longitudinal groove corresponds to the fourth rib. The right groove is chiefly pos- 
terior; it begins below the termination of the posterior vena cava. The intermediate groove 
begins below the posterior end of the left auricle, and in its descent inclines gradually to the left 
side of the apex. 
The vena hemiazygos usually unites with the terminal part of the great cardiac 
vein, thus forming a trunk which opens into the right atrium below the posterior 
vena cava. 
Two bones, the ossa cordis, develop in the aortic fibrous ring. The right one 
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