210 CIRCULATORY SYSTEM. 



which getting forwards near the sternum, are distributed upon 

 the pectoralis major, and upon the contiguous muscles. The 

 last of these branches, according to M. H. Cloquet, goes trans- 

 versely across the ensiform cartilage, and, having anastomosed 

 with its fellow, descends between the peritoneum and the linea 

 alba to the suspensory ligament of the liver. 



On a line generally wi^h the anterior extremity of the fifth 

 rib, the internal mammary divides into two principal branches; 

 the most exterior of which, descending along the cartilaginous 

 margin of the thorax, is distributed in small twigs to the origin 

 there of the diaphragm and of the transverse muscle of the ab- 

 domen. The internal branch reaches the posterior face of the 

 rectus abdominis muscle, and is dispersed upon it: some of its 

 branches go as low as the umbilicus, to anastomose there with 

 the epigastric artery. 



5. The Posterior Cervical Artery (Jlrleria Cermcalis Poste- 

 rior, Transversa) is of a very unsettled origin, but comes most 

 frequently either from the subclavian itself, or from the inferior 

 thyroid. It is but small in some subjects, owing to its place 

 being supplied by branches from the adjoining arteries. 



It crosses horizontally the root of the neck on the outer face 

 of the scaleni muscles above the subclavian artery. It gets 

 under the anterior margin of the trapezius, and is there divided 

 into two principal branches; the ascending one is spent upon 

 the trapezius and the levator scapulae; the other descends along 

 the base of the scapula, and is spent in ramifications upon the 

 rhomboidei and the serratus major muscles. Several branches 

 of minor size and importance are sent off from the posterior 

 cervical artery to the muscles on the back of the neck and 

 thorax. 



The Subclavian Artery having sent off the preceding branches, 

 then escapes from the thorax between the scaleni muscles, and 

 gets to the arm-pit between the first rib and the subclavius 

 muscle. The trunk of it is then continued downwards through 

 the axilla, and at the inner side of the arm to the elbow joint. 



From the scaleni muscles to the elbow its relative position is 

 as follows: When it first appears between the scaleni, it is 

 bounded above and behind by the collected fasciculi of the ax- 



