212 THE MUSCLES 



1. Iliac Fascia or Lumbo-iliac Aponeurosis. (Fig. 108, A.) 



This is a very resisting fibrous expansion, covering the great and iliac 

 psoas muscles. Attached, inwardly, to the tendon of the small psoas, out- 

 wardly to the angle and external border of the ilium, this aponeurosis, as it 

 extends forwards over the great psoas, degenerates into cellular tissue. 

 Behind, it also becomes attenuated in accompanying the two muscles it 

 covers until near their insertion into the internal trochanter of the femur. 

 Its external or inferior face receives, posteriorly, the insertion of the crural 

 arch, and gives attachment to the long adductor of the leg ; for the re- 

 mainder of its extent, it is covered by the peritoneum. 



2. Great Psoas Muscle. (Fig. 108, 1.) 



Synonyms. Sublumbo-trochantineus Girard. Psoas J3ourgelat. (Lumbo-femoral- 

 Leyh. Psoas magnus PercivalL] 



Form Situation. This is a long muscle, flattened above and below at its 

 anterior extremity, prismatic in its middle, and terminated in a cone at its 

 posterior extremity. It lies beneath the transverse processes of the lumbar 

 vertebrae. 



Structure. Almost entirely fleshy, this muscle is formed of fasciculi, 

 very delicate in texture, directed backwards, and long in proportion to their 

 superficial and deep situation. They all converge to a tendon which is 

 enveloped by the iliac muscle, and is confounded with it. 



Attachments. The great psoas is attached: 1, By the anterior extremity 

 of its fleshy fasciculi to the bodies of the last two dorsal and the lumbar 

 vertebrae, except the hindermost, and to the inferior face of the two last ribs 

 and the transverse processes of the lumbar vertebrae ; 2, By its posterior 

 tendon to the internal trochanter, in common with the psoas iliacus. 



Relations. Below, with the pleura, the superior border of the diaphragm, 

 the lumbo-iliac aponeurosis, which separates it from the peritoneum and 

 the abdominal viscera situated in the sublumbar region; above, with the 

 two last internal intercostals, the quadratus, and the intertransversales 

 muscles ; inwardly, with the small psoas and the internal branch of the 

 iliac psoas ; outwardly, for its posterior third, with the principal branch of 

 the latter muscle. 



Action. A flexor and rotator of the thigh outwards when its fixed point 

 is the loins, this muscle also flexes the lumbar region when the thigh is 

 a fixed point. It is, therefore, one of the agents which determine the arching 

 of the loins, and which operate, during exaggerated rearing or prancing, in 

 bringing the animal into a quadrupedal position again. 



3. Iliac Psoas Muscle. (Fig. 108, 3, 4.) 



Synonyms. Ilio-trochantineus Girard. (Leyh divides this muscle into two por- 

 tions, which he describes as the great and middle ilio-femoralis. Iliacus Percivall.) 



Form Situation Direction. This is a very strong, thick, and prismatic 

 muscle, incompletely divided into two unequal portions by the groove for 

 the reception of the tendon of the great psoas : an external portion, somewhat 

 considerable in size ; and an internal, small. These two muscular portions 

 lie at the entrance to the pelvis, on the inner face of the ilium, in an oblique 

 direction downwards, backwards, and inwards. 



Structure. It is almost entirely fleshy. The fasciculi forming it are 



