ARTERIES 



453 



aeration, the blood from each hemibranch passes into an efferent 

 branchial artery (ef. br\ which joins with its fellow of the same cleft 

 (except in the case of ef. br?}, and thus forms a loop surrounding the 

 cleft, the two halves of adjacent loops being connected in the middle by 

 a commissural vessel. From the upper ends of each of the four loops 

 arises an epibranchial artery (ep. br) which is connected with the dorsal 



ct.tza 



d.c 



FIG. i2i. The heart and branchial arteries of Scy Ilium, from the side. 

 af. br. ! 5 , afferent branchial arteries ; ati. auricle ; c. a. conus arteriosus ; c/. 1 5 , 

 branchial clefts ; cor. coronary artery ; d. ao. dorsal aorta ; d. c. dorsal carotid 

 artery ; ef. br.^ 9 , efferent branchial arteries ; ep. br.^ 4 , epibranchial arteries ; 

 inn. mandibular artery ; sp. spiracle ; ,y. cl. subciavian artery ; s. v. sinus venosus ; 

 v. ventricle ; v. ao. ventral aorta ; v. c. ventral carotid artery. 



aorta (d. ao}, the blood from the last hemibranch passing into the fourth 

 loop. 



From the dorsal end of the first efferent branchial, a dorsal carotia 

 artery (d. c} is given off: this passes forwards and inwards, gives off a 

 branch to the upper jaw and snout, and then runs inwards in a groove on 

 the skull- floor, which it penetrates in the middle line so as to reach the 

 cranial cavity. A vessel arises from the middle of the first efferent 

 branchial, and supplies the pseudobranch, from which the blood is col- 

 lected by a ventral carotid artery (v. c}, which passes through the orbit 

 into the cranium, giving off branches to the brain and anastomosing 

 with the dorsal carotid. From the ventral end of the first efferent 

 branchial a small mandibular artery (mn) passes to the lower jaw. The 



