438 



THE MUSCULAE SYSTEM. 



SEMI- 

 SPINALIS 



CAPITIS 



LONGISSIMUS 



form a narrow ligamentous band which connects the last rib to the iliac crest 

 between the muscles of the back on the one hand and those of the abdominal wall 

 on the other. The middle layer is a fascia which stretches laterally from the ends 

 of the transverse processes of the lumbar vertebrae, between the sacrospinalis behind 

 and the quadratus lumborum muscle in front. The anterior layer is attached to the 



lumbar vertebrae near the bases of 

 their transverse processes. It covers 

 the anterior surface of the quadratus 

 lumborum muscle, and separates it from 

 the psoas major. The psoas fascia is 

 continuous at the lateral border of the 

 psoas major muscle with the anterior 

 layer of the lumbo-dorsal fascia. At 

 the lateral borders of the quadratus 

 lumborum and sacrospinalis muscles 

 the three layers blend together, and 

 give partial origin to the obliquus 

 internus and transversus abdominis 

 muscles. 



THE MUSCLES OF THE BACK. 



The muscles of the back are ar- 

 ranged in four series according to their 

 attachments : (1) vertebro - scapular 

 and vertebro -humeral, (2) vertebro- 

 costal, (3) vertebro -cranial, and (4) 

 vertebral. They are in irregular 

 strata, the most superficial muscles 

 having the most widely spread attach- 

 ments. 



The first series of muscles of the 

 back, connecting the axial skeleton to 

 the upper limb, have already been 

 described. They are arranged in two 

 layers: (1) trapezius and latissimus 

 dorsi superficially ; (2) levator scapulae, 

 and rhomboidei, deep to the trapezius 

 (p. 368). 



The remaining muscles are almost 

 entirely axial, and may be divided into 

 four groups : (1) serrati posteriores, 

 superior and inferior ; splenius capitis 

 and splenius cervipis ; (2) sacrospinalis 

 and semispinalis capitis ; (3) semi- 

 spinalis dorsi and cervicis (transverso- 

 spinales) ; and (4) the small deep 

 muscles (rotatores, interspinales, inter- 

 transversarii, and suboccipital mus- 

 cles). They extend from the sacrum 

 to the head, forming a cylindrical 

 column in the loin, filling up the 



vertebral groove in the thorax, and giving rise to the muscular mass at the back 



of the neck. 



First Group. 



M. Serratus Posterior Superior. The serratus posterior superior has a 

 membranous origin from the ligamentum nuchse and the spines of the last cervical 



ILIOCOSTALIS 

 LUMBORUM 



FIG. 391. SCHEMATIC EEPBESENTATION OF THE PARTS 

 OF THE LEFT SACROSPINALIS MUSCLE. 



