MYOLOGY. 63 



Insertion. Transverse processes of lumbar vertebrae and outer 

 surfaces of fifteen or sixteen last ribs. 



Action. Extends vertebral column and pulls ribs forward in 

 expiration. 



Nerve. Superior dorsal. 



COMMON INTERCOSTAL. 



Origin. Runs from external surface of one rib to the next ; 

 the anterior fasciculus; into the last cervical vertebra. 

 Action. Depresses ribs. 

 Nerve. Intercostal. 



TRANSVERSE SPINOUS OF BACK AND LOINS. 



Origin. Lateral lip of sacrum, articular tubercles of lumbar 

 and transverse processes of dorsal vertebrae. 



Insertion. Spinous process of sacral, lumbar, dorsal and last 

 cervical vertebrae. 



Action. Extensor of spine. 



Nerve. Superior dorsal. 



COSTAL REGION. 



Here are found 54 muscles: 



(i) 17 external intercostals; (2) 17 internal intercostals; (3) 

 17 supercostals; (4) serratus magnus; (5) costo-transversalis, 

 and (6) triangularis sterni. 



EXTERNAL INTERCOSTALS. 



Origin. Downward and backward from posterior border of 

 rib in front. 



Insertion. Anterior border of rib behind. 

 Action. Muscles of inspiration. 

 Nerve. Intercostal. 



INTERNAL INTERCOSTALS. 



Origin. Downward and forward, crossing preceding from 

 inner and anterior border of rib behind. 

 Insertion. Posterior border of rib in front. 

 Action. Muscles of expiration. 

 Nerve. Intercostals. 



