356 MUSCLES AND FASCIA. 



plied by the external posterior branches of the lumbar and dorsal nerves ; the 

 Cervicalis Ascendens, Trans versa! is Colli, Trachelo-mastoid, and Spinalis Cer- 

 vicis, by the external posterior branches of the cervical nerves ; the Cornplexus 

 by the internal posterior branches of the cervical nerves, the suboccipital and 

 great occipital. 



FIFTH LAYER. 



Semispinalis Dorsi. Extensor Coccygis. 



Semispinalis Colli. Intertransversales. 



Multifidus Spinse. Eectus Capitis Posticus Major. 



Rotatores Spinae. Rectus Capitis Posticus Minor. 



Supraspinales. Obliquus Capitis Superior. 



Interspinales. Obliquus Capitis Inferior. 



Dissection. Remove the muscles of the preceding layer by dividing and turning aside the 

 Complexus ; then detaching the Spinalis and Longissimus Dorsi from their attachments, dividing 

 the Erector Spinae at its connection below to the sacral and lumbar spines, and turning it out- 

 wards. The muscles filling up the interval between the spinous and transverse processes are 

 then exposed. 



The Semispinalis muscles (Fig. 228) connect the transverse and articular pro- 

 cesses to the spinous processes of the vertebrae, extending from the lower part 

 of the dorsal region to the upper part of the cervical. 



The Semispinalis Dorsi consists of thin, narrow, fleshy fasciculi, interposed 

 between tendons of considerable length. It arises by a series of small tendons 

 from the transverse processes of the lower dorsal vertebrae, from the tenth or 

 eleventh to the fifth or sixth ; and is inserted by five or six tendons into the 

 spinous processes of the upper four dorsal and lower two cervical vertebrae. 



The Semispinalis Colli, thicker than the preceding, arises by a series of ten- 

 dinous and fleshy points from the transverse processes of the upper four dorsal 

 vertebrae, and from the articular processes of the lower four cervical vertebra ; 

 and is inserted into the spinous processes of four cervical vertebrae, from the 

 axis to the fifth cervical. The fasciculus connected with the axis is the largest, 

 and chiefly muscular in structure. 



Relations. By their superficial surface, from below upwards, with the Longis- 

 simus Dorsi, Spinalis Dorsi, Splenius, Complexus, the profunda cervicis artery, 

 the princeps cervicis artery, and the posterior cervical plexus of nerves. By 

 their deep surface, with the Multifidus Spinae. 



The Multifidus Spinse consists of a number of fleshy and tendinous fasciculi, 

 which fill up the groove on either side of the spinous processes of the vertebrae, 

 from the sacrum to the axis. In the sacral region, these fasciculi arise from the 

 back of the sacrum, as low as the fourth sacral foramen, and from the aponeu- 

 rosis of origin of the Erector Spinae ; in the iliac region, from the inner surface 

 of the posterior superior spine, and posterior sacro-iliac ligaments; in the lum- 

 bar and cervical regions, from the articular processes; and in the dorsal region, 

 from the transverse processes. Each fasciculus, ascending obliquely upwards 

 and inwards, is inserted into the lamina and whole length of the spinous process 

 of one of the vertebrae above. These fasciculi vary in length : the most super- 

 ficial, the longest, pass from one vertebra to the third or fourth above; those 

 next in order pass from one vertebra to the second or third above; whilst the 

 deepest connect two contiguous vertebrae. 



Relations. By its superficial surface, with the Longissimus Dorsi, Spinalis 

 Dorsi, Semispinalis Dorsi, and Semispinalis Colli. By its deep surface, with the 

 laminae, and spinous processes of the vertebrae, and with the Rotatores Spinae 

 in the dorsal region. 



The Eotatores Spinse are found only in the dorsal region of the spine, beneath 

 the Multifidus Spinoe; they are eleven in number on each side. Each muscle is 

 small and somewhat quadrilateral in form ; it arises from the upper and back 

 part of the transverse process, and is inserted into the lower border and outer 



