THE THORACIC MUSCLES. 



541 



Nerve-Supply. — From the anterior divisions of the eighth cervical and the 

 first to the eleventh thoracic nerves. 



Action. — To assist in drawing the ribs upward. Acting from the ribs, they 

 will assist in bending the spinal column backward and laterally towards the same side 

 and in rotating it towards the opposite side. 



5. Serratus Posticus Superior (Fig. 539). 



Attachm'ents. — The superior posterior serratus is a quadrangular, flat muscle 

 which arises by a flat tendon from the lower part of the ligamentum nuchae and from 

 the spinous processes of the seventh cervical and upper two or three thoracic ver- 



Complex 



Splenius capitis 



_ L'' — T rachelo-mastoid 



I 



1 Inttrnal pt^ygoid 



Coiiiplexus 



Bi\ enter cervicis 



Levator atiguli scapu 

 Serratus posticus sup 



Trapezius — ^ . 

 (cut) /' 



\'I( cervical spinous process 



Complexus 



Scalenus posticus 



Vertebral-3 

 aponeurosis 



Accessorius 



Ilio-costalis 



Longissimus dorsi 

 Dorsal, cervical, and thoracic muscles. 



tebrae. Its fibres are directed downward and laterally to be inserted into the outer 

 surface of the second to the fifth ribs, lateral to their angles. 



Nerve- Supply. — From the anterior divisions of the first to the fourth thoracic 

 nerves. 



Action. — To raise the ribs to which it is attached and accordingly assist in 

 inspiration. 



6. Serratus Posticus Inferior (Fig. 559). 



Attachments. — The inferior posterior serratus arises by a broad but thin 

 tendon from the posterior layer of the lumbo-dorsal fascia from about the level of 

 the second lumbar to that of the tenth or eleventh thoracic vertebra. Its fibres are 



