MUSCLES OF THE BODY. I39 



162, 8) belongs in this group, but since it moves the leg it is 

 described with the muscles of the pelvic limbs. 



M. psoas minor (Fig. 162, 9, page 398). — This muscle lies 

 along the ventral surface of the vertebral column, next to the 

 peritoneum, and extends from the thoracic vertebrae to the 

 ilium. 



Origin usually by five heads, from the caudal border of the 

 centra of the last two (or one) thoracic and first three (or four) 

 lumbar vertebra:. These heads also serve as origin for a part 

 of the iliopsoas, and are closely united at their origin with the 

 quadratus lumborum. They unite to form an, at first, rather 

 large flat muscle, which rapidly becomes smaller caudad, 

 finally forming a slender tendon which is insci-tcd on the ilio- 

 pectineal line, just craniad of the acetabulum. 



Relations. — Dorsolateral surface with the quadratus lum- 

 borum and iliopsoas (Fig. 162, 8). Ventral surface with the 

 pleura and diaphragm near the origin ; with the peritoneum 

 caudad. 



Action. — Flexes the back in the lumbar region. 



M. quadratus lumborum. — A flat muscle lying on the 

 ventral surface of the transverse processes of the lumbar verte- 

 brae. Craniad it has origin on the ventral surface of the last 

 two thoracic vertebrje, and by a few fibres from the last rib. 

 The muscle passes caudad, lying on the lateral side of the 

 psoas minor (I'ig. 162, n), and becomes attached to each of the 

 transverse processes of the lumbar vertebra:. Caudad the 

 muscle passes into a strong flat tendon which is inserted into 

 the anterior inferior spine of the ilium. 



Relations. — Dorsal surface with the transverse processes 

 and the intertransverse muscles. Ventral and medial surfaces 

 with the psoas minor (Fig. 162, 9) and iliopsoas (Fig. 162, s). 



Action. — Bends the vertebral column sideways. 



B. Muscles on the Ventral Side of the Neck (Fig. 

 65, page 109). — M. sternomastoideus (Fig. 65, g\ Fig. 

 68, c). — The sternomastoid (sternal portion of the human 

 sternocleidomastoid) is a flat band one to three centimeters 

 wide extending from the cranial end of the manubrium and the 

 midventral line craniad of it to the lambdoidal ridge. 



