96 ANATOMY AND PHYSIOLOGY 



oblique; and the transversus muscles. They occupy the space 

 between the eight lower ribs above, and the ilium and pubes 

 below. Being broad and flat they do not possess tendons of the 

 usual kind, but many of their muscle fibers terminate in layers of 

 white fibrous tissue called aponeuroses, which continue to the 

 median line, there blending with the layers from the opposite side. 

 This produces a firm interlacing of white fibers called the linea 

 alba or -white line, stretched between the ensiform appendix above 

 and the body of the pubes below. It is a very strong and impor- 

 tant line, through which, a little below the middle, the umbilical 

 cord passes in the fetus; this point in the linea alba is indicated 

 by the umbilicus, or navel. 



The external oblique (Fig. 79) is the outermost of the three 

 layers. Origin. The lower eight ribs. Direction of fibers, 

 downward and forward. Insertion. Some fibers on the crest 

 of the ilium; others in an aponeurosis which passes to the linea 

 alba. 



Nerves. Lower thoracic. 



Special point. The lower border of the aponeurosis of this muscle between 

 the spine of the ilium and the spine of the pubes is firm and unyielding, easily 

 felt, and important to be recognized; it is called the inguinal ligament (or 

 Poupart's ligament] . 



The internal oblique (Fig. 80) lies underneath the external 

 oblique. Origin. The lumbar fascia, crest of the ilium, and 

 lateral half of the inguinal ligament. Direction of fibers, upward 

 and forward. Insertion. Some fibers on the lower three ribs, 

 others in the linea alba, and the lowest ones on the crest of the 

 pubes. 



Nerves. Lower thoracic and first lumbar. 



The transversus (Fig. 80) is the innermost of the three layers. 

 Origin. The lower six ribs, the lumbar fascia, crest of the ilium, 

 and lateral half of the inguinal ligament. Direction of fibers, 

 transversely across the side of the abdomen, toward the front. 

 Insertion. In the linea alba, and the crest of the pubes. On 

 the pubes it is blended with that part of the internal oblique which 

 is attached to the same bone, making the conjoined tendon. 



Nerves. Lower thoracic and first lumbar. 



Action, of the three broad muscles. They compress the 



