308 Abdominal Muscles and Fascice 



Additional anterior relations are the kidney, ureter, and renal and 

 spermatic vessels, peritoneum and colon, and, lower down, the external 

 iliac and common femoral artery. Behind it are the quadratus lum- 

 borum, the anterior division of last dorsal nerve, the anterior lumbar 

 arteries, the brim of pelvis, capsule of hip-joint, and the bursa. Below 

 Poupart's ligament the internal circumflex artery intervenes between 

 its inner border and the pectineus. 



The iliacus and psoas are supplied by the anterior crural nerve. 



The course taken by spinal abscess is greatly controlled by the 

 arrangements of fasciae and muscles. Pus from caries of the lower 

 dorsal vertebrae may find its way beneath the internal arcuate liga- 

 ment into the substance of the psoas beneath the vertebral part of 

 the iliac fascia and may descend beneath Poupart's ligament into the 

 front of the thigh. Pus from lumbar caries may pass at once into 

 that sheath, or, working behind the psoas, may enter the sheath of 

 quadratus lumborum (see p. 305), and point on the outer side of the 

 erector spinae (lumbar abscess) ; or it may infiltrate itself between the 

 large, flat muscles to point against the linea semilunaris, or it may 

 wander into the inguinal canal and so reach the scrotum. From the 

 lower lumbar vertebrae the matter may course under or through the 

 psoas, to get beneath that piece of fascia which binds down the iliacus, 

 and will then bulge in the inguinal region (iliac abscess), or, possibly, 

 on the front of the thigh. Or, sinking in the pelvis, it may find exit 

 by the great sacro-sciatic notch (gluteal abscess) or by the ischio-rectal 

 fossa. When suppuration occurs between the transversalis, muscle and 

 the transversalis fascia, or between that fascia and the peritoneum, there 

 is nothing to prevent the abscess extending across the middle line. 



When the sheath of the psoas is filled by pus there is a fulness in 

 the iliac fossa, the furrow over Poupart's ligament being partially 

 effaced, and fluctuation being obtainable between the base of Scarpa's 

 triangle and the inguinal region that is, beneath Poupart's ligament. 

 The thigh is kept flexed so as to diminish the pressure on the lumbar 

 plexus. The presence of matter in the psoas gradually determines 

 the absorption of the muscular tissue, and at last the sheath contains 

 only the lumbar plexus bathed in pus. Psoas abscess is almost in- 

 variably the result of spinal caries. 



The sub-peritoneal fascia is a loose layer of connective tissue 

 and fat between the peritoneum and the transversalis and iliac fascia;. 

 It is thick in the loins, where it forms a soft bed for the kidneys. There 

 is a good deal of it also in the iliac fossae, where an unimportant 

 horizontal fold of it, the septum crurale, blocks the innermost com- 

 partment of the crural sheath. A loose investment from it surrounds 

 the cord, and gives an unimportant covering to inguinal hernia. (The 

 cover ngs of the hernia are, therefore, skin, two layers of superficial 

 fascia, intercolumnar cremasteric, and infundibuliform fascia: and sub- 

 peritoneal fat.) 



