The =levatores costarum= and =rectus thoracis= present no special
features.
The =external intercostal= muscles are absent under the serratus anticus
and posticus and the digitations of the external oblique.
The =internal intercostals= are thick between the cartilages of the
sternal ribs.
The =retractor costæ= and the =transversus thoracis= resemble those of
the horse; the latter extends back to the eighth cartilage and fuses
with the transversus abdominis.
The =diaphragm= has seven costal digitations on each side, the posterior
ones being attached to the ribs at some distance (ca. one-third to
one-fourth of rib-length) from the costo-chondral junction. The line of
attachment reaches the latter at the tenth rib, and passes along the
eighth cartilage to the xiphoid process. The tendinous center is more
rounded than in the horse. The crura are well developed. The right crus
is very large, and is perforated by the extensive slit-like opening for
the œsophagus, which is median in position, and lies about two and
one-half to three inches (ca. 6 to 8 cm.) below the twelfth thoracic
vertebra. The hiatus aorticus is between the crura.