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 backward. There is a 

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

 ually diminishes toward the lower ends of the sjDaces. 



Seventh ccri'ical vertebra- ' 

 First thoracic vertebra 



Section of scapula 



Intertransversales 



Intercostal f 

 nerves (. 



Retractor co 



Intertransverse liga 



Ilio-lumhar ligament. 



Levatores costarum 



External 



\ intercostal 



ni uscles 



TraTfiUriabs 

 iw^tarani 



Outtr border of lon- 

 gtssinius dorsi 



- Ezternal angle 

 of ilium 



Fig. 184. — Dors.\l and Lumbar Regions of Horsi , 1)ot?«~\i \n-w (\ftei ^(tmnlf/. \flas d. Anat. d. Pferdes.) 



Relations. — 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 



