_Relations._--Outer surface with the latissimus dorsi (Fig. 68, _p_), and at the origins with the intercostales externi (Fig. 73, _m_). Inner surface with the intercostales interni (Fig. 69, _k_) at the origin and with the intercostales externi (Fig. 69, _i_), iliocostal (Fig. 69, _h_), longissimus dorsi (Fig. 69, _f_), and the caudal end of the spinalis dorsi (Fig. 69, _g_). [Illustration: FIG. 73.--BODY MUSCLES EXPOSED AFTER REMOVAL OF THE FORELIMB AND THE MUSCLES SHOWN IN FIG. 68. _a_, M. occipitoscapularis (cut); _b_, M. splenius; _c_, M. levator scapulæ ventralis (cut); _d_, M. cleidomastoideus (cut); _e_, M. longus capitis; _f_, M. scalenus (_f′_, middle division; _f″_, dorsal division; _f‴_, ventral division; _f_, cervical portion); _g_, M. longissimus capitis; _h_, M. levator scapulæ (cut); _i_, M. serratus anterior (cut); _j_, M. transversus costarum; _k_, M. rectus abdominis (_k′_, its tendon); _l_, M. serratus posterior superior; _m_, M. intercostales externi; _n_, M. serratus posterior inferior; _o_, M. obliquus abdominis internus; _p_, lumbodorsal fascia.] _Action._--Assists the serratus posterior superior. =M. transversus costarum=, or =sternocostalis externus= (Fig. 73, _j_).--This is a thin muscle applied to the cranial part of the side of the thorax, covering the cranial end of the rectus abdominis (_k_). _Origin_ by tendon from the side of the sternum between the attachments of the third and sixth ribs. The muscle passes dorsocraniad to its _Insertion_ on the first rib and the lateral portion of its costal cartilage. _Relations._--Outer surface with the pectoralis minor (Fig. 65, _o_). Inner surface with the scalenus (Fig. 73, _f‴_), the rectus abdominis (Fig. 73, _k_), and the intercostales externi (Fig. 73, _m_). At its insertion it is united with a portion of the scalenus (Fig. 73, _f‴_). _Action._--Draws the sternum forward. =Mm. levatores costarum.=--Small muscles having _origin_ on the transverse processes of the thoracic vertebræ, passing caudoventrad, and becoming _inserted_ on the angle of the rib lying immediately caudad of the origin. They are continuous with the external intercostals. _Relations._--Outer surface with the longissimus dorsi (Fig. 69, _f_), and craniad with the iliocostal (Fig. 69, _h_). Inner surface with the internal intercostals (Fig. 69, _k_). _Action._--Pull the ribs dorsocraniad.