///A BACK. 



397 



strengthen the same region. So we will see that from the transverse processes 

 of all the dorsal vcrtebnt to the spines of all the dorsals and cervicals there- 

 is a continuous, uninterrupted plane of oblique muscular fibres. (Fig. 285.) 

 They are called semispinalcs dorsi and colli. They are synergistic physiologi- 

 cally to the multifidus spinaj only a larger edition of the same. Their function 

 is extension and lateral rotation. 



Note, again, there is an upward continuation of this same muscular arrange- 

 ment to the head the eoniple.viis, a semispinalis capitis. (Fig. 283.) It arises 

 from the transverse prm-esses of the upper six thoracic and last cervical, and is 



Trapeiius 



INION OR EXTERNAL-OCCIPITAL PROTUBERANCE 



SUPERIOR NUCHAL LINE 



Occipito-fro, Italia 



MIDDLE NUCHAL LINE 



Sterno-maatoid 



Bplenius capitis 



Hcctus cap. post. mln. 

 Reetus cap. post. maj. 



Superior oblique 



INFERIOR NUCHAL LINE 



Reotua capitis laterally 



POSTERIOR OONOYLOIO 

 FORAMEN 



JUGULAR PROCESS 



BASI-OCCIPITAL 



FIG. 278. THE OCCIPITAL. (External view.) 



inserted into the occipital bone. Its action is extension and lateral rotation of 

 the head. 



The above are the simple movements of the vertebral column. Complex 

 movements may be had by combination of different simple movements. I have 

 spoken of the mechanism in advance of the dissection, to inspire the student to 

 greater care in his work. 



NERVES THAT SUPPLY THE BACK. 



1. Tkc long sttbscapiilnr nerve to the latissimus dorsi (brachial plexus). 



2. The spinal aceessory nerve to the trapezius (twelfth cranial nerve). 



3. The snboccipital ncn<e to the complexus, recti, and oblique muscles. 



4. Mnsetttar brandies from tlie een'ical plexus to the rhomboids and levator 

 an^uli scapulae. 



5. Posterior divisions of the spinal nerves, thirty-one pairs to other muscles. 



6. The great oceipital nerve, to the complexus muscle and to the scalp. 

 Scheme for the Posterior Divisions of the Spinals. All except the first 



cervical divide into internal anil external branches ; the internal branches sup- 

 ply the sixth and seventh layers, the external branches the remainder ; they 



