THE MUSCLES OF THE THORAX 



241 



Insertion. — The anterior borders and external surfaces of the succeeding ribs. 



Action. — To draw the ribs forward in inspiration. 



Structure. — The fibers are directed downward and V)ackward. There is a 

 considerable admixture of tendinous tissue. The thickness of the muscles grad- 

 ually diminishes toward the lower ends of the spaces. 



Seventh cervical vertebra- " 



Section of scapald 



Intel trdiihursales 



Intercostal f 

 nerve.'^ { 



Retractor 

 IntertransverbC liqannittb <•'''( 

 Ilio-lumbar ligament 



Levaiores costarum 



1 External 

 \ intercostal 

 \uscles 



•v^' 





7 ? (nisvcrsalis 

 ( o itarurn 



M 



■ Outer border of lo7i- 

 gissimns dor si 



-- External angle 

 of iliiitn 



Fig. 184.— Dorsal .\xr> Lfmbar Regions of Horse. Dorsal View. (After Schmaltz, Atlas <1. Anat. d. Pferdes.) 



72e?aiions.— Superficially, the serratus magnus, latissimus dorsi, serratus anticus 

 and posticus, longissimus dorsi, transversalis costarum, rectus thoracis, deep 

 pectorals, obliquus abdominis externus, and panniculus; deeply, the internal inter- 

 costals and (in the upper part of the spaces) the intercostal vessels and nerves. 



Blood-supply. — Intercostal and internal thoracic arteries. 



Nerve-supply. — Intercostal nerves. 

 16 



