300 THE MUSCLES OF THE OX 



vertebrjB. It is traversed by the roots of the brachial plexus, which partially 

 divide it into a small dorsal and a large ventral part. The brachial vessels lie 

 below the latter. The scalenus dorsalis (s. supracostalis) arises usually on the 

 second, third, and fourth ribs, and ends on the transverse processes of the third 

 to the sixth cervical vertebrae. 



The rectus capitis anterior major arises on the third to the sixth cervical 

 transverse processes, and blends at its insertion with the sterno-mastoideus and 

 the mastoid portion of the mastoido-humeralis. 



The rectus capitis anterior minor is larger than in the horse. 



The rectus capitis lateralis and longus colli reseml)le those of the horse. 



The intertransversales are large. From the sixth cervical vertebra forward 

 they form a muscular mass (M. intertransversarius longus) which is inserted into 

 the wing of the atlas. 



B. LATERAL GROUP 



The splenius is thin. It arises directly from the first three or four thoracic 

 spines, and ends by a thin tendon on the occipital bone, the wing of the atlas, 

 and the transverse process of the axis, blending with the mastoido-humeralis, 

 trachelo-mastoideus, and omo-transversarius. The remaining muscles present no 

 very marked differential features. 



Muscles of the Thorax 



The levatores costarum number ten or eleven pairs. 



The diaphragm presents several important differential features. Its slope is 

 much steeper and its width is greater than in the horse. The costal attachment 

 extends almost in a straight line from the upper fourth of the last rib to the junc- 

 tion of the eighth rib with its cartilage, and along the latter to the sternum. The 

 mid-line slopes from the twelfth thoracic vertebra obliquely as far as the vena 

 cava, beyond which it is almost vertical. The right crus divides into two branches, 

 which circumscribe the oesophageal opening, unite below, and then spread out in 

 the tendinous center. The left crus is small. The oesophageal opening is situated 

 about four to five inches (10 to 12 cm.) below the eighth thoracic vertebra, a little 

 to the left of the median plane. The foramen venae cavae is a little more ventral 

 and almost in the median plane. The other muscles resemble those of the horse. 



Muscles of the Back and Loins 



The serratus anticus is very thin. It is inserted on the fifth to the eighth ribs. 

 It may be reduced to two or three digitations or may be absent. The serratus 

 posticus is usually inserted on the last three or four ribs. 



The transversalis costarum (Iliocostalis) has a distinct lumbar portion which 

 is attached to tlio lumbar transverse processes and the external angle of the ilium. 



The longissimus resembles that of the horse, but it is more fleshy anteriorly, 

 and the spinalis dorsi is clearly distinguishable from the common mass. In the 

 lumbar region the tendons meet across the summits of the s])ines. 



Intertransversales are present in the back, and interspinales in the back and 

 loins. 



MUSCLES OF THE TAIL 



These resemble those of the horse; the coccygeus is, however, much more 

 developed. 



