28G 



Muscles of the Back. 



Insertion of Ihe m. latissimus dorsi 

 M. serratus posterior inferior 



Processus spinosus vertebrae thoracalis XII 

 I M. latissimus dorsi 



II I I 



] I Tendon of origin of the ni. i I 



I j transversus abdominis Fascia lunibodorsalis ; 

 I I M. obliquus internus (posterior layer) 



' Crista iliaca abdominis M. glutaeus maximus 



M. obliquus externus abdominis 



I 



I M. obliquus 



externus abdominis 

 I Trigonum lumbale [Petiti] 

 M. glutaeus medius 



331. Muscles of the lumbar region (l^Mayer), viewed from 



behind. (,(_)ii the left the m. latissimus dorsi has been removed.) [Text see also pp. 287 and 288.] 



M. latissimus dorsi (see also Figs. 316, 329, 330 and 343). Form: hat, triangular, 

 thin. Position: in the lower part of the back and lateral region of the thorax, being partly 

 covered above by the ra. trapezius. Origin: tendinous from the posterior layer of the fascia 

 lumbodorsalis , from tbe proc. spinosus of the 6'^ thoracic vertebra on downward, from the 

 crista iliaca and, by three or four fleshy digitations, from the external surface of the three or 

 four lowermost ribs. Insertion: the fibers run, converging, lateralward, the upper fibers 

 more transversely, the lower almost straight upward ; they lie on the lateral wall of the thorax 

 close to the m. serratus anterior, fuse with the lower margin of the m. teres major, wind 

 ardund it to its anterior surface and become attached by a flat tendon to the crista tuberculi 

 niiniiris humeri. Between these two muscles, in this situation, Ues the bursa m. latissimi 

 dorsi (see Fig. 345). Action: it draws the aim medianward and backward; it draws the 

 shoulder-blade medianward and downward. Innervation: n. thoracodorsalis. 



M. rhoinboidcus major (see Figs. 329 and 330). Form: flat, quadrangular. 

 Position: upper part of the back, covered by the m. trapezius. Origin: tendinous from 

 spinous processes and interspinal ligaments of the pt 4th thoracic vertebra. Insertion: the 

 fibres run parallel downward and lateralward to the margo vertebrahs scapidae. Action: it 

 draws the shuulder-bladt^ medianward and u])war(l and rotates it at the same time so that 

 the aiigulus inferior scapulae is turned medianward. Innervation: n. dorsalis scapulae. 



M. rhomboideus minor (see Fig. ?.30), often only indistinctly separable from the 

 prt>ceding muscle. F(rm: flat, obl^.ig-quadrangular. Position: directly on the upper margin 

 of the preceding muscle. Origin: tendinous from the lig. nuchae and the spinous processes 

 of the two lower cervical vertebrae. Insertion: like that of the preceding muscle, just above 

 the same. Action and innervation: same as for the preceding muscle. 



