MUSCLES OF THE BACK. 



203 



Fig. 115* 



spinalis dorsi, are associated under the name of erector spinse. They 

 occupy the lumbar and dorsal portion of the back. The remaining four 

 are situated in the cervical region. 



The SACRO-LUMBALIS and LONGISSIMUS DORSI arise by a common origin 

 from the posterior third of the crest of the ilium, from the posterior surface 

 of the sacrum, and from the lumbar vertebne ; opposite the last rib a line 

 of separation begins to be perceptible between the two muscles. The 

 sacro-lumbalis is inserted by separate tendons into the angles of the six 

 lower ribs. On turning the muscle a little out- 

 wards, a number of tendinous slips will be seen 

 taking their origin from the ribs, and terminating 

 in a muscular fasciculus, by which the sacro- 

 lumbalis is prolonged to the upper part of the 

 thorax. This is the musculus accessorius ad 

 sacro-lumbalem : it arises from the angles of the 

 six lower ribs, and is inserted by separate ten- 

 dons into the angles of the six upper ribs. 



The longissimus dorsi is inserted into all the 

 ribs, between their tubercles and angles. 



The SPINALIS DORSI arises from the spinous 

 processes of the two upper lumbar and three 

 lower dorsal vertebrae, and is inserted into the 

 spinous processes of all the upper dorsal verte- 

 bra ; the two muscles form an ellipse, which 

 appears to enclose the spinous processes of all 

 the dorsal vertebrse. 



Relations. The erector spinse muscle is in 

 relation by its superficial surface (in the lumbar 

 region) with the conjoined aponeurosis of the 

 trans versalis and internal oblique muscle, which 

 separates it from the aponeurosis of the serratus 

 posticus inferior, and longissimus dorsi; (in the 

 dorsal region) with the vertebral aponeurosis, 

 which separates it from the latissimus dorsi, 

 trapezius, and serratus posticus superior, and 

 with the splenius. By its deep surface (in the 

 lumbar region) with the multifidus spinse, trans- 

 verse processes of the lumbar vertebras, and with the middle layer of the 

 aponeurosis of the transversalis abdominis, which separates it from the 

 quadratus lumborum ; (in the dorsal region) with the multifidus spinse, 

 semi-spinalis dorsi, levatores costarum, intercostal muscles, and ribs as 

 far as their angles. Internally or mesially with the multifidus spinse, and 

 semi-spinalis dorsi, which separate it from the spinous processes and 

 arches of the vertebrse. 



The two layers of aponeurosis of the transversalis abdominis, together 



* The foarth and fifth, and part of the sixth layer of the muscles of the back. 1. The 

 common origin of the erector spinae muscle. 2. The sacro-lumbalis. 3. The longissi- 

 mus dorsi. 4. The spinalis dorsi. 5. The cervicalis ascendens. 6. The transversalis 

 colli. 7. The trachelo-mastoideus. 8. The complexus. 9. The transversalis colli, 

 showing its origin. 10. The semi-spinalis dorsi. 11. The semi-spinalis colli. 12. The 

 rectus posticus minor. 13. The rectus posticus major. 14. The obliquus suoerioi. 

 15. The obliquus inferior. 16. The multifidus spinae. 17. The levatores costarum 

 IS. Intertransversales. 19. The quadratus lumborum. 



