34 



U.S. NATIONAL MUSEUM BULLETIN 2 73 



This fact, which I could not verify, would correspond to the presence 

 of a splenius cervicis in the howling monkey. 



Nerve supply: A branch from the dorsal primary ramus of CIII. 



Long System 



Its muscles form a longitudinal mass which covers the deep oblique 

 system and, more laterally, lies over the rib cage. Two of them, m. 

 iliocostalis and m. longissimus, have a common origin in the lumbar 

 region from a tough, extensive, and tendinous sheet, the aponeurosis 

 sacrospinalis (figs. 11, 12, 13). M. spinalis lies medially to the other 

 two and has a separate origin from the same lamina (figs. 11, 12). 

 The longissimus is continued into the tail by m. extensor caudae 

 lateralis and the two abductors. 



The aponeurosis sacrospinalis (figs. 11, 13): Strong tendinous 

 fascicles arise from (1) the spines of most thoracic, all lumbar, sacral, 

 and the first two caudal vertebrae, and (2) the corresponding ligamenta 

 supraspinalla. They all run craniolaterally and are joined by similar 

 fibers arising from (3) the dorsal half of the iliac crest and the region 

 of the posterosuperior iliac spine. In this manner a shiny lamina is 

 formed over the long muscles of the back. It extends laterally a little 



® 



Figure 12. — Section at the level of T9 showing arrangement of thoracolumbar fascia 

 (1, anapophysis; 2, metapophysis; 3, m. spinalis; 4, m. longissimus; 5, m. iliocostalis; 6, 

 thoracolumbar fascia; 7, sagittal septum; 8, m. latissimus dorsi; 9, m. serratus posterior 

 inferior). 



