THE ABDOMEN, EXTERIOR. 451 



Transversalis Abdominis. Figs. 91, 94. 



Origin. By fleshy slips from the inner surfaces of the 

 six lower costal cartilages, interdigitating with the origins 

 of the diaphragm. From the lumbar fascia, and the ante- 

 rior three-fourths of the inner lip of the crest of the ilium, 

 and from the outer third of Poupart's ligament. 



Insertion. By the conjoined tendon as given. See page 

 447. Into the whole length of the linea alba, which it 

 helps to form. 



The Lumbar Fascia. Fig. 76. Diag. 29. 



Consists of three layers. The anterior, from the bases 

 of the transverse processes of the lumbar vertebrae. The 

 middle, from the tips of the same processes. The pos- 

 terior, by the broad sheath of the erector spinae muscle 

 from the spinous processes and the supraspinous ligaments 

 of the lumbar and adjoining dorsal and sacral vertebrae. 

 Between the first and second layers is the quadratus lum- 

 borum ; between the second and third, the erector spinae. 

 That portion of the anterior layer extending from the first 

 lumbar vertebra to the tip of the last rib is called the 

 ligamentum arcuatum externum. 



Lying upon the tranversalis muscle are the nerves which 

 are passing forward to supply the abdominal muscles. 

 They are the lower six intercostal and the iliohypogastric 

 and ilio-inguinal from the first lumbar. 



Along with the nerves are found branches from the 

 intercostal and lumbar arteries. The deep circumflex iliac 

 artery gives off several large branches which pass upward 

 between the internal oblique and the transversalis muscles. 

 In the dissection of the preceding muscles it has been 

 noticed that the fibres of the three layers run obliquely or 

 at right angles to each other. The fibres of the trans- 



