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. 



Actio7i. — Extensor of spine. 



Nerve. — Superior dorsal. 



COSTAL REGION. 



Here are found 54 muscles : — 



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

 (3) 1 7 supercostals ; (4) serratus magnus ; (5) costo-transver- 

 salis, 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. 

 Nei-ve. — Intercostal. 



INTERNAL INTERCOSTALS. 



Origin. — Downward and forward, crossing preceding from 

 inner and anterior border of rib behind. 

 Insertion. — Posterior border of rib in front. 

 Actio7i. — Muscles of expiration. 

 Nerve. — Intercostals. 



