MUSCLES OF THE ABDOMEN. 191 



from its attachment to the ribs above, and to the crest of the ilium 

 and Poupart's ligament below. It should be divided behind by a 

 vertical incision extending from the last rib to the crest of the ilium, 

 as its lumbar attachment cannot at present be examined. The 

 muscle is then to be turned forwards. Some degree of care will 

 be required in performing this dissection, from the difficulty of dis- 

 tinguishing between this muscle and the one beneath. A thin layer 

 of cellular tissue is all that separates them for the greater part of 

 their extent. Near the crest of the ilium the circumflex ilii artery 

 ascends between the two muscles, and forms a valuable guide to 

 their separation. Just above Poupart's ligament they are so closely 

 connected that it is impossible to divide them. 



The transversalis is the internal flat muscle of the abdomen ; it is 

 transverse in the direction of its fibres, as is implied in its name. It 

 arises from the outer third of Poupart's ligament, from the internal 

 lip of the crest of the ilium, its anterior two thirds ; from the spinous 

 and transverse processes of the lumbar vertebrae,* and from the inner 

 surfaces of the six inferior ribs, indigitating with the diaphragm. 

 Its lower fibres curve downwards, to be inserted, with the lower 

 fibres of the internal oblique, into the pectineal line, and fo*m the 

 conjoined tendon. Throughout the rest of its extent it is inserted 

 into the crest of the os pubis and linea alba. The lower fourth of 

 its aponeurosis passes in front of the rectus to the linea alba ; the 

 upper three-fourths, with the posterior lamella of the internal oblique, 

 behind it. 



The posterior aponeurosis of the transversalis divides into three 

 lamellae ; anterior, which is attached to the bases of the transverse 

 processes of the lumbar vertebrae ; middle, to the apices of the trans- 

 verse processes ; and posterior, to the apices of the spinous processes. 

 The anterior and middle lamellae enclose the quadratus lumber urn 

 muscle ; and the middle and posterior, the erector spinae. The union 

 of the posterior lamella of the transversalis with the posterior aponeu- 

 rosis of the internal oblique, serratus posticus inferior, and latissimus 

 dorsi, constitutes the lumbar fascia. 



Relations. By its external surface with the internal oblique, the 

 internal surfaces of the lower ribs, and internal intercostal muscles. 

 By its internal surface with the transversalis fascia, which separates 

 it from the peritoneum, with the psoas magnus, and with the lower 

 part of the rectus and pyramidalis. The spermatic cord and oblique 

 inguinal hernia pass beneath the lower border, but have no direct re- 

 lation with it. 



To dissect the rectus muscle, the sheath should be opened by a 

 vertical incision extending from over the cartilages of the lower 

 ribs to the front of the os pubis. The sheath may then be dissected 

 off and turned to either side : this is easily done excepting at the 

 lineae transversae, where a close adhesion subsists between the muscle 



* From the transverse processes of the last dorsal and four superior lumbar verte- 

 brae. G. 



