48 



U.S. NATIONAL MUSEUM BULLETIN 2 73 



female. In the other male it takes place on ribs 2, 3, and 4 on the right 

 side, but 3, 4, and 5 on the left. 



Sirena (1871) claims that the costal ending includes all five first 

 ribs and does not describe an origin from C 1. In other respects his 

 information coincides with mine but he refers to the muscle as m. 

 scalenus posticus. 



Nerve supply: Branches from the anterior rami of C III to VI. 



M. scalenus medius accesorius (fig. 16): This triangular muscle is 

 attached by its apex to the tip of the transverse process of C 7. Its 

 strong fleshy fibers radiate out toward the upper surface of the first 

 rib where they are inserted bet\\een the sulcus subclavius (this 

 insertion is not marked in the bone) and the angle. The accesorius 



Figure 17. — Lateral view of the trunk and neck (1, m. scalenus brevis posterior; 2, m. scale- 

 nus medius; 3, m. rectus abdominis; 4, m. obiiquus cxternus abdominis; 5, fascia thoraco- 

 lumbalis; 6, m. scrratus posterior inferior; 7, m. serratus anterior, pars caudalis; 8, m. 

 subscapularis; 9, m. scrratus anterior, pars cranialis; 10, ni. atlantoscapularis posterior. 



