138 THE MUSCLES. 



specimens is united with that muscle (Fig. 162, 11) in the 



cat. 



Origin along the ventral half of the medial surface of the 

 ilium, caudad of the sacrum. The fibres pass caudad and are 

 inserted by a flat tendon into the ventral surface of the caudal 

 vertebrae, from the second or third to about the seventh. 



Relations. — Lateral surface with the gluteus maximus 

 and abductor caudae internus (Fig. 68, zv). Medial surface with 

 the levator ani (Fig. 162, 11), with which this muscle may be 

 partly united. 



Action. — The two muscles together flex the tail. 



M. flexor caudae longus (Fig. 162, 12; Fig. 113, c, page 

 270). 



Origin on the ventral surface of the last lumbar vertebra, 

 of the sacrum, and of the transverse processes of the caudal 

 vertebrae. Caudad the muscle forms long, strong tendons 

 which are inserted on the ventral surface of the tail. 



Relations. — Lateral surface with the ilium, the gluteus 

 maximus, the abductor caudae internus, the iliocaudalis, and the 

 skin of the tail. Dorsally it touches in the caudal region the 

 abductor caudae externus (Fig. 68, %v), medially the flexor caudae 

 brevis (Fig. 162, 13). 



Action. — Flexes the tail. 

 C) M. flexor caudae brevis (Fig. 162, 13). 



Origin on the ventral surface of the caudal vertebrae, from 

 the first to the seventh or eighth. The principal head comes 

 from the first vertebra. The bundles thus formed pass caudad 

 and are inserted each into the ventral surface of a vertebra 

 some distance caudad of the origin. The muscle extends to 

 about the tenth caudal vertebra, and its most caudal parts are 

 closely interconnected with the flexor caudai longus. 



Relations — Lateral edge with the flexor caudae longus. 

 Medial edge in the sacral region with the levator ani (Fig. 162, 

 11) and the iliocaudalis (Fig. 162, ii') ; in the caudal region 

 with the muscle of the opposite side. 



Action. — Flexes the tail. 



2. Muscles on the Ventral Side of the Vertebral Column. 

 A. Lumbar and Thoracic Regions. — The iliopsoas (Fig. 



