190 MYOLOGY. 



Costal Region. 



The muscles of this region are those which cover the lateral 

 aspect of the thoracic cavity ; some of them are attached to the 

 anterior limb, three of which we describe the first, as it is 

 necessary in dissection to cut through them, and remove or 

 deflect the limb in order to expose fully the deeper-seated 

 muscles. The following are the muscles of the region : — 



Superficialis costarum. 

 Trans versalis costarum. 

 Levatores costarum. 



Trapezius dorsalis. 

 Rhomboideus brevis. 

 Latissimus dorsi. 

 Serratus magnus. 



Intercostales. 



TRAPEZIUS DOESALIS. 



{Dorso-acromicdis. ) 

 (Pl. IL 14.) 



Situated on the side of the withers, this muscle is flat and 

 triangular, being almost the reversed counterpart of the cervical 

 trapezius. The two form the trapezius onuscle. It is aponeu- 

 rotic at its superior border, while its belly is fleshy, terminating 

 in a flat tendon. 



Origin. — Superiorly, from the supraspinous ligament, and 

 from the third dorsal spine back to the tenth or eleventh. The 

 fibres converge downwards and forwards, over the superior costa 

 of the scapula, and join the cervical portion. 



Insertion. — The tubercle on the spine of the scapula. 



Relation. — Externally with the skin and panniculus ; internally 

 with the rhomboideus brevis, postea-spinatus, and latissimus 

 dorsi. 



Action. — To draw upwards and retract the scapula. 



rhomboideus brevis. 



(^Dorso-suhscapularis. ) 

 (Pl. IIL 12.) 



Deep-seated, on the side of the withers above the scapula, it 

 is flat and square ; the fibres extend downwards, and are entirely 

 fleshy. 



