178 MYOLOGY, OR ANATOMY OF MUSCULAR SYSTEM 



Third Layer. Serrati Muscles. 1. M. Serratus Posticus 

 Superior. Origin, by a thin aponeurosis from .two, rarely 

 three, upper dorsal spines, supraspinous ligament, seventh 

 cervical spine, lower part of ligamentum nuchse; fibers pass 

 down and out; inserted by four slips into the upper border 

 and outer surfaces of the second, third, fourth, and fifth ribs 

 beyond their angles. 



2. M. Serratus Posticus Inferior (broader than the above). 

 Origin, by part of the lumbodorsal aponeurosis from first two 

 lumbar and last two or three dorsal spines; passing up and 

 out; inserted by four slips into the lower borders of the last 

 four ribs up to the origin of the latissimus dorsi. 



3. Mm. Splenii. Named from strap-like action binding 

 down underlying parts; rise from lower half of neck and upper 

 half of back. 



(a) M. Splrniiix Capitis. Origin, ligamentum nwlw over 

 third, fourth, fifth, and sixth cervical spines, from seventh 

 cervical and first two dorsal spines; insertion, outer surface 

 and posterior margin of mastoid process, outer part of superior 

 curved line to insertion of trapezius. 



(6) M. Splenius Cermcis (colli). Origin, below the above 

 from the third, fourth, fifth dorsal spines, not lower than the 

 sixth; insertion, with slips of the levator anguli scapulae into 

 the tips of the transverse process of the first and second, often 

 third, cervical vertebrae. 



The splenii are covered in part by the trapezius, rhomboidei, 

 and superior serratus; the complexus comes to view internal 

 to them. 



Nerves. Trapezius by the spinal accessory, third, and fourth 

 cervical nerves; rhomboidei by the fifth cervical nerve; teres 

 major by the lower subscapular nerve (sixth and seventh 

 cervical); latissimus dorsi by the long subscapular nerve 

 (seventh and eighth cervical); the serrati by the intercostals 

 or the upper slip of the serratus posticus superior by the cervical 

 plexus; the splenii by the posterior spinal nerve. 



Actions. Trapezius, upper part supports shoulder, raises 

 point of the shoulder by rotation of the scapula, acts in forced 

 respiration; middle part adducts the scapulae, helps elevate 

 the shoulder, throws the chest out; inferior part would alone 

 depress and carry the scapulae in, but in concert with the 

 upper two-thirds of the muscle it raises the acromion and 



