416 THE MUSCLES AND FASCIA. 



extent. It is thin above, and becomes gradually thicker below as it approaches the 

 crural arch. 



The portion covering the Psoas is attached, above, to the ligamentum arcuatum 

 internum ; internally, by a series of arched processes to the intervertebral sub- 

 stances and prominent margins of the bodies of the vertebrae, and to the upper part 

 of the sacrum, the intervals so left, opposite the constricted portions of the bodies, 

 transmitting the lumbar arteries and veins and filaments of the sympathetic cord. 

 Externally, above the crest of the ilium, this portion of the iliac fascia is continu- 

 ous with the anterior lamella of the lumbar fascia (see page 342), but below the 

 crest of the ilium it is continuous with the fascia covering the Iliacus. 



The portion investing the Iliacus is connected externally to the whole length 

 of the inner border of the crest of the ilium, and internally to the brim of the true 

 pelvis, where it is continuous with the periosteum ; and at the ilio-pectineal emi- 

 nence it receives the tendon of insertion of the Psoas parvus, when that muscle 

 exists. External to the femoral vessels, this fascia is intimately connected to the 

 posterior margin of Poupart's ligament, and is continuous with the fascia transver- 

 salis. Immediately to the outer side of the femoral vessels the fascia iliaca is pro- 

 longed backward and inward from Poupart's ligament as a band, the ilio-pectineal 

 ligament, which is attached to the ilio-pectineal eminence. This ligament divides 

 the space between Poupart's ligament and the innominate bone into two parts, the 

 inner of which transmits the femoral vessels, the outer the ilio-psoas and the anterior 

 crural nerve (Fig. 166). Internal to the vessels the iliac fascia is attached to the 

 ilio-pectineal line behind the conjoined tendon, where it is again continuous with the 

 transversalis fascia ; and, corresponding to the point where the femoral vessels pass 

 into the thigh, this fascia descends behind them, forming the posterior wall of the 

 femoral sheath. This portion of the iliac fascia which passes behind the femoral 

 vessels is also attached to the ilio-pectineal line beyond the limits of the attach- 

 ment of the conjoined tendon; at this part it is continuous with the pubic portion 

 of the fascia lata of the thigh. The external iliac vessels lie in front of the iliac 

 fascia, but all the branches of the lumbar plexus behind it ; it is separated from 

 the peritoneum by a quantity of loose areolar tissue. 



The Psoas magnus (Fig. 253) is a long fusiform muscle placed on the side of 

 the lumbar region of the spine and margin of the pelvis. It arises from the front 

 of the bases and lower borders of the transverse processes of the lumbar vertebrae 

 by five fleshy slips ; also from the sides of the bodies and the corresponding inter- 

 vertebral substances of the last dorsal and all the lumbar vertebrae. The muscle 

 is connected to the bodies of the vertebrae by five slips ; each slip is attached to 

 the upper and lower, margins of two vertebrae, and to the intervertebral substance 

 between them, the slips themselves being connected by the tendinous arches which 

 extend across the constricted part of the bodies, and beneath which pass the lumbar 

 arteries and veins and filaments of the sympathetic cord. These tendinous arches 

 also give origin to muscular fibres, and protect the blood-vessels and nerves from 

 pressure during the action of the muscle. The first slip is attached to the con- 

 tiguous margins of the last dorsal and first lumbar vertebrae; the last to the 

 contiguous margins of the fourth and fifth lumbar vertebrae, and to the interver- 

 tebral substance. From these points the muscle passes down across the brim of 

 the pelvis, and, diminishing gradually in size, passes beneath Poupart's ligament, 

 and terminates in a tendon which, after receiving nearly the whole of the fibres of 

 the Iliacus, is inserted into the lesser trochanter of the femur. 



Relations. -In the lumbar region : by its anterior surface, which is placed 

 behind the peritoneum, with the iliac fascia, the ligamentum arcuatum internum, 

 the kidney, Psoas parvus, renal vessels, ureter, spermatic vessels, genito-crural 

 nerve, and the colon ; by its posterior surface, with the transverse processes of the 

 lumbar vertebrae and the Quadratus lumborum, from which it is separated by the 

 anterior lamella of the lumbar fascia. The lumbar plexus is situated in the 

 posterior part of the substance of the muscle. By its inner side the muscle is in 

 relation with the bodies of the lumbar vertebrae, the lumbar arteries, the ganglia 



