60 OUTLINES OF ANATOMY. 



Erector Spinae Middle Division : 

 Trachelo-mastoid : 



Origin. Insertion. 

 Structure of the middle division. Nerve-supply. Action. Relations. 



Inner division, 445. (440-1) 

 Spinalis dorsi : 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 



Variations of the erector spinas and its divisions. 



Divide the trachelo-mastoid about two inches below its insertion, reflect the lower portion of the muscle 

 to the origin, then remove it ; carefully raise the upper portion and expose the occipital artery in the 

 second part of its course. 



The occipital artery : 



Second part of its course, 518-19-20. (511-12) 

 Branches: Mastoid branch. 



Princeps cervicis, superficial branch. 

 Muscular branches. 

 Complexus, 446; Fig. 306. (441) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. Variations. 



Divide the complexus transversely near the middle, carefully raise and reflect each portion, noting the 

 nerves passing through it. Expose the deep branch of the princeps cervicis, and the posterior divisions 

 of the spinal nerves. 



Princeps cervicis, deep branch, 520. (511-12) 



Deep cervical branch from the superior intercostal, 551 ; Fig. 342. (541) 

 Deep cervical vein, 652. (639) 



Posterior primary divisions of the spinal nerves, 825-6-7-8 ; Fig. 452. (806-7-8-9) 

 Cervical nerves: 



Internal branches. External branches. 

 Posterior division of the second cervical nerve. 



Great occipital nerve. 

 Thoracic nerves: Internal branches. 

 External branches. 

 Lumbar nerves: Internal branches. 



External branches of the upper three nerves, 

 of the fourth lumbar nerve, 

 of the fifth lumbar nerve. 



Arteries of the cervical, thoracic, and lumbar regions : 

 Cervical region : 



Princeps cervicis, 520. (511-12) 

 Deep cervical branch, 551. (541) 



Muscular branches, from the second portion of the vertebral, 542. (532) 

 Thoracic region : From intercostal arteries : 



Dorsal branch, 582; Fig. 362. (571-2) 

 (ii) Muscular branch. 

 Lumbar region : From lumbar arteries : 



Dorsal branch, 588. (577) 



The veins accompany the arteries and terminate in the intercostal or lumbar veins, in 

 the thoracic or lumbar regions. 



Demonstrate the middle layer of the lumbar fascia, 434. (430). Divide the erector spins at its origin 

 and remove the muscle, together with its divisions, in order to expose the underlying muscles to advantage. 



Semispinalis dorsi, 446-78; Fig. 308. (443) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 

 Semispinalis colli, 448 ; Fig. 308. (443) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 

 Multifidus spinae, 448; Fig. 308. (443-4) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. 



Follow the branches of the sacral and coccygeal nerves through the multifidus spinae, cutting away the 

 muscle to expose the nerves. The entire muscle should then be removed. 



