234 LABORATORY MANUAL OF HUMAN ANATOMY 



Short Muscles of the Back (First, Second, and Third Layers). 



(Vide Spalteholz, Figs. 338, 339, and 340.) 

 Cut away the attachments of the M. spinalis dorsi and reflect 

 the M. longissimus dorsi lateralward. Reflect the M. longissimus 

 capitis lateralward and upward. The M. semispinalis is now 

 exposed. Clean it thoroughly. While cleaning the M. semi- 

 spinalis capitis avoid injuring the posterior cutaneous rami of 

 the cervical nerves (rami cutanei posteriores Nn. cervicalium) 

 emerging from the substance of the muscle near the middle line. 



(a) Semispinal muscle (M. semispinalis). (Cf. Spalteholz, Fig. 338.) 



(aa) Semispinal muscle of back (M. semispinalis dorsi). 



(ab) Semispinal muscle of neck (M. semispinalis cervicis) (O. T. 



semispinalis colli). 



(ac) Semispinal muscle of head (M. semispinalis capitis) (0. T. 



complexus). 



Establish exact form, position, origin, insertion, action, and in- 

 nervation of each. 



Cut away the attachments of the M. semispinalis from the ver- 

 tebral spines and from the transverse processes, and study 



(b) Multifidus ("much-divided") muscle (M. multifidus). 



What is its origin? Establish insertion, action, and innervation. 



Cut away the M. multifidus and expose the third layer of short 

 muscles. Observe in the sacral region the posterior rami of the 

 sacral and coccygeal nerves (rami posteriores Nn. sacralium et 

 N. coccygei). 



(c) Rotator muscles (Mm. rotatores). 



(ca) Long rotator muscles (Mm. rotatores longi). 



(cb) Short rotator muscles (Mm. rotatores breves). 



(d) Elevators of the ribs (Mm. levatores costarum). 



(da) Short elevators of the ribs (Mm. levatores costarum breves). 



(db) Long elevators of the ribs (Mm. levatores costarum longi). 



(e) Interspinal muscles (Mm. interspinales) . 



(f) Intertransverse muscles (Mm. intertransversarii) . 



(fa) Cervical. 



(faa) Anterior (Mm. intertransversarii anteriores). 



(fab) Posterior (Mm. intertransversarii posteriores) . 



(fb) Lumbar. 



(fba) Medial (Mm. intertransversarii mediales). 



(fbb) Lateral (Mm. intertransversarii laterales). 



Short Muscles of the Neck. (Cf. Spalteholz, Fig. 341). 



Carefully clean the surface of the following muscles : 



(a) Larger posterior straight muscle of head (M. rectus capitis posterior 



major). 



(b) Lesser posterior straight muscle of head (M. rectus capitis posterior 



minor). 



(c) Superior oblique muscle of head (M. obliquus capitis superior). 



(d) Inferior oblique muscle of head (M. obliquus capitis inferior). 



