218 
ANATOMY OF THE RABBIT. 
1. Muscles arising from the ventral surface of the posterior 
thoracic and lumbar vertebrae and inserted on the pelvic girdle, 
or on the lesser trochanter of the femur. These muscles are chiefly 
distinguished by their vertebral position, on account of which and 
the fixed condition of the pelvic girdle they combine the characters 
of vertebral and appendicular muscles. 
(a) 
(b) 
(c) 
(d) 
The psoas minor. Origin: Bodies of the four posterior 
lumbar vertebrae. Insertion: Pecten of the pubis. The 
flat, pointed tendon forms a square cross with a dorsal 
(sacral) continuation of the inguinal ligament, which is 
stretched transversely from the middle of the inguinal liga- 
ment to the centre of the body of the first sacral vertebra, 
and on which the tendon is also inserted. 
It is necessary to divide the inguinal ligament and reflect its sacral 
continuation, together with the tendon of the psoas minor. 
The psoas major. Origin: Internal surfaces of the bases of 
the last three ribs and bodies of the corresponding thoracic 
vertebrae; also the lumbar vertebrae. Insertion: Lesser 
trochanter. 
The iliacus. Origin: Bodies of the last lumbar and first 
sacral vertebrae, extending to the sacroiliac union. Inser- 
tion: With the psoas major on the lesser trochanter. The 
two muscles together form the iliopsoas. 
The lumbar portion of the lumbosacral plexus, beginning with 
the fourth lumbar nerve, lies on the ventral surface of the psoas major 
and between the latter and the iliacus. The fifth lumbar is the chief 
root of the femoral nerve (p. 225), the trunk of which may be traced 
from a position between the two muscles distad over the dorsal surface 
of the inguinal ligament to the medial surface of the thigh. The remain- 
ing four nerves crossing the dorsal body-wall obliquely are the twelfth 
thoracic and first three lumbar. 
The psoas major should be freed at its lateral margin and turned 
toward the middle line, the fourth lumbar nerve being divided. 
The quadratus lumborum. Origin: Bodies of the 
posterior five thoracic vertebrae and the bases of the corres- 
ponding five ribs; bodies and transverse processes of the 
lumbar vertebrae. Insertion: Triangular processes of six 
lumbar vertebrae and the posterior ventral angle of the iliac 
wing, together with the adjacent portion of its medial sur- 
face. 
