The =pericardium= is attached by two fibrous bands (Ligamenta
sternopericardiaca) to the sternum opposite the facets for the sixth
costal cartilages; 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.
[Illustration:
FIG. 467.—HEART OF OX, LEFT VIEW.
]
The =heart= of the adult ox has an average weight of about 5½ to 6
pounds (ca. 2.5 to 2.7 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.
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.
The heart is situated more to the left of the median plane than in the
horse and is opposite to the third, fourth, and fifth ribs when it is
contracted. It has extensive contact with the lateral wall of the thorax
on the left side, but none on the right side, where a considerable
thickness of lung covers the pericardium.[178]
Two bones, the =ossa cordis=, develop in the aortic fibrous ring. The
right one is in apposition with the atrio-ventricular rings and is
irregularly triangular in form. Its left face is concave and gives
attachment to the right posterior cusp of the aortic valve. The right
surface is convex from before backward. The base is superior. The
posterior border bears two projections separated by a notch. It is
usually a little more than an inch (ca. 4 cm.) in length. The left bone
is smaller and is inconstant. Its concave right border gives attachment
to the left posterior cusp of the aortic valve. There is a large fleshy
moderator band in the right ventricle.