MUSCLES OF THE BODY. 139 
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 vertebrz 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 zzserted 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- 
bre. Craniad it has origin on the ventral surface of the ‘last 
two thoracic vertebrz, and by a few fibres from the last rib. 
The muscle passes caudad, lying on the lateral side of the 
psoas minor (Fig. 162, 9), 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, 8). 
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. 
