The abdominal tunic is practically absent.
The =obliquus abdominis externus= has an extensive fleshy portion. It
arises from the last eight or nine ribs and the lumbo-dorsal fascia.
The =obliquus abdominis internus= arises from the external angle of the
ilium and the lumbo-dorsal fascia. The fibers have an almost vertical
direction, and there is a fleshy attachment to the last rib.
The =rectus abdominis= is attached by a long tendon on the first five or
six costal cartilages, and by fleshy fibers on the xiphoid cartilage. It
has three to six indistinct tendinous inscriptions.
The =transversus abdominis= presents no special features except that the
posterior part of its aponeurosis splits into two layers which include
the rectus between them.