226 THE VASCULAR SYSTEM. 



reached at the ciliary processes. In its course the artery sup- 

 plies : — 



a. Muscular branches, given off at the point where the artery 

 reaches the eyeball. 



/3. Two arteries [AÂ. ci/iareft) to the choroid, given off at the 

 same point as the foregoing'. 



y. Two arteries to the iris. 



Ô. The Art. hyaloidea, the terminal portion of the ophthalmic 

 artery. (For further description of these vessels, see Eye.)]. 



2. The systemic arch [Bnctns aorticvs), (Figs. 132, 143, and 

 145 77) is the middle arch of the three; it arises from the middle 

 canal of the .Ductus arteriosus, and winds obliquely round the 

 oesophagus between the MM. petrohyoidei I and // towards the 

 vertebral column, which it reaches at about the level of the 

 sixth vertebra. The right systemic arch is continued as the 

 dorsal aorta, the left arch communicates with it merely by a 

 small opening, and is then continued as the coeliaco-mesenteric 

 artery. 



Branches of the systemic arch : — 



a. The laryngeal artery [Arteria larynged), (Fig. 146 Ig) arises 

 from the inner border of the systemic arch before it reaches the 

 oesophagus ; it passes forwards and inwards to be distributed in 

 the larynx and pharynx. According to Briicke this artery possesses 

 a valve at its point of origin. 



pj g b. The oesophageal arteries [Arteriae 



oesopliageae) pass from the upper part of the 

 arch to the dorsal surface of the oesophagus. 

 c. The oecipito-vertebral artery (Ecker), 

 [Ai-t. occipito-vertebralis), (Fig. 147 o,v) [arises 

 from the systemic arch immediately in 

 front of the transverse process of the second 

 vertebra^ and ascends immediately in contact 

 with the body of the first vertebra, which it 

 separates from the MM. iutertransversarii 

 capitis and the sympathetic cord]. Immedi- 

 ately under the most antei'ior portion of the 

 M. longissimns dorsi the artery divides into 

 two branches, the vertebral and occipital 

 arteries : — 

 (i) The vertebral artery [Arteria vertehralis or supra-vertehralis 



