146 EQUINE ANATOMY. 



n:ites in forming the iiftli alone or with another branch 

 from the first posterior intercostal. ■ 



2 The SUPERIOR CERVICAL. — Synonyms. Cervico-mus- 

 cular ; runs outside the thorax through the first inter- 

 costal space, passing upwards and forwards under the 

 complexus major muscle, reaches the second cervical 

 vertebrse and anastomoses with the occipito-muscular 

 and the dorsal arteries. It gives for collateral branches 

 the first intercostal, muscular and tegumentary brandies 

 to the superi'.)r cervical regions. 



3. The VERTEBRAL. — Passiug inside the first rib, out- 

 side the trachea and the inferior cervical ganglion, and 

 under the transverse process of the seventh cervical 

 vertebrae, enters the trachelian foramen, runs forwards 

 and upwards to the atlas, where it anastomoses with 

 the occipital. Its external, superior and inferior collat- 

 erals go to the muscles of the neck ; its internal to form 

 the median spinal. 



4. The INTERNAL THORACIC OR MAMMARY. — Descending 

 inside the first rib to the sternum, then backwards upon 

 its superior face, it terminates at the base of the xyphoid 

 cartilage by the anterior abdominal, which passes out- 

 side the thorax under that cartilage, on the superior 

 face of the rectus abdominis muscle, where it ramifies 

 and finally anastomoses with tlie posterior abdominal, 

 and by the asternal artery, which lies inside the cartil- 



