180 ANATOMY OF THE RABBIT. 
Examine the following muscles, proceeding in a similar manner: 
(a) The internal oblique muscle (m. obliquus internus 
abdominis). Origin: The inguinal ligament, a second sheet 
of the lumbodorsal fascia, and the posterior four ribs. 
Insertion: The linea alba. The fibres pass downward and 
forward. The ventral aponeurosis is much broader than 
that of the external oblique. Near the mid-ventral line 
it is split into two leaves, coniaining between them the thin 
rectus abdominis muscle. 
(b) The transverse muscle (m. transversus abdominis). 
Origin: Seven posterior ribs, a third sheet of the lumbo- 
dorsal fascia, and the inguinal ligament. Insertion: The 
linea alba. The fibres are directed downward and slightly 
backward. 
The rectus abdominis muscle. Origin: Lateral border 
of the sternum, including the xiphoid process; also the 
ventral surfaces of the second to seventh costal cartilages. 
Insertion: At the anterior end of the pubic symphysis. It 
is a thin, strap-like muscle, enclosed by the aponeurosis 
of the internal oblique, and separated from its fellow of the 
opposite side by the linea alba. 
(c 
SS’ 
The artery passing forward, for the most part in this muscle, is the 
inferior epigastric, a branch of the external iliac (p. 203). It anastomoses 
withthe internal mammary (p. 257). It gives off the external spermatic 
artery, a small vessel which perforates the abdominal wall and extends 
backward, supplying the sac of the testis in the male and ending in the 
female in the wall of the vulva. 
5. Divide the remaining portion of the wall on the left side, and 
its whole thickness on the right, by a transverse incision, so that 
the viscera are fully exposed. Note on the internal surface of 
the wall the smooth serous investment here forming the parietal 
peritoneum (peritonaeum parietale). 
