MUSCLES OF THE TRUNK. 



271 



4. Small Psoas Muscle (Psoas Parvus) (Fig. 165, 2). 



Synonyms. — Psoas of tlie loins— Bourgelat. Sublumbo-pubialis, or sublumbo-iliacus, 

 according to Girard. (Psoas parvus — Percivall. Tlie lombo-iliacus of Leyh.) 



Situation — Form — Structure. Placed at the inner side of the psoas magnus, 

 very much elon,ii:ated, and semipennifonn in shape, this muscle is terminated 

 behind by a flattened tendon, and is composed of fleshy fibres, the lonpjest of 

 which are anterior. These fasciculi are all directed backwards and outwards to 

 gain the tendon. 



Attachment fi. — 1. To the bodies 

 of the three or four last dorsal, and 

 to all the lumbar vertebrae, by the 

 anterior extremity of its fleshy fibres. 

 2. To the ilio-pectineal line and the 

 lumbo-iliac aponeurosis, by the pos- 

 terior extremity of its tendon. 



Relations. — By its inferior face 

 with the pleura, the superior border 

 of the diaphragm, the aorta or pos- 

 terior vena cava, and the great 

 sympathetic nerve ; by its upper face, 

 with the psoas magnus. It is tra- 

 versed, near its vertebral insertions, 

 by niunerous vascular and nervous 

 branches. 



Actions. — It flexes the pelvis on 

 the spine, when the loins are the 

 fixed point ; but should the pelvis be 

 fixed, it arches or laterally inclines 

 the lumbar region. It is also the 

 tensor muscle of the lumbo-iliac 

 aponeurosis. 



Fig. 166. 



DEEP MUSCLES OF THE SUBLUMBAR REGION. 



1, Quadratus Inniborum ; 2, 2, intertransversales ; 

 3, small retractor muscle of the last rib — a de- 

 pendent of the small oblique of the abdomen. 



5. Square Muscle of the Loras (Quadratus Lumborum) (Fig. 166, 1). 



Synonyms. — Sacro-costalis — Girard. (Sacro-lumbalis — Percivall. Quadratus lumborum of 

 Man.) 



Situation — Form — Structure — Attachments. — This muscle is comprised between 

 the transverse processes of the lumbar region and the psoas magnus, is elongated 

 from before to behind, flattened above and below, and divided into several very 

 tendinous fasciculi. The principal fasciculus, situated outwardly, takes its origin 

 from the sacro-iliac ligament, near the angle of the sacrum, and extends directly 

 forward to gain the posterior border of the last rib, after being attached by its 

 upper face to the summits of the transverse processes of the lumbar vertebrae. 

 The other fasciculi are longer as they are anterior ; they leave the internal border 

 of the first, and are directed obhquely forward and inward, to be fixed into the 

 transverse processes of the majority of the lumbar vertebras, and the inner face 

 of the two or three last ribs. 



Relations. — By its upper face, with the intertransversales, the small retractor 



