374 A MANUAL OF ANATOMY. 



toid ; the external column, by the iliocostalis, accessorius, 

 and cervicalis ascendens. 



The Erector Spinee. 



Origin. From the lowest two or three dorsal and all 

 the lumbar and sacral spines, from the back of the sacrum, 

 from the posterior one-fifth of the crest of the ilium and the 

 posterior iliac spines. 



Insertion. Its fibres pass into the spinalis dorsi (inner), 

 longissimus dorsi (middle), and iliocostalis, or sacrolum- 

 balis (external) muscles. 



Nerve Supply. The posterior branches of the lumbar 

 nerves. 



Action. See below. 



The Spinalis Dorsi. (Inner column.) 



Origin. The inner portion of the erector spinae. 



Insertion. The spinous processes of the upper dorsal 

 vertebrae (four to nine). 



Nerve Supply. The posterior branches of the dorsal 

 nerves. 



Action. To extend the thoracic portion of the spine. 



The Long-issimus Dorsi. (Middle column.) 



Origin. The middle portion of the erector spinae. 



Insertion. (Inner tendons.) The transverse processes 

 of the dorsal, and the accessory tubercles of the lumbar 

 vertebrae. 



(Outer set.) To the transverse processes of the lumbar 

 vertebrae, to the lower ten ribs external to their tubercles. 



Nerve Supply and Action. See below. 



Transversalis Cervicis. (Middle column.) 



Origin. From the transverse processes of the upper 

 four or five dorsal vertebrae. 



