238 AN INTRODUCTION TO ZOOLOGY 



mid- ventral line, where it penetrates the floor of the cranium with 

 its fellow, through the carotid foramen just behind the pituitary 

 fossa. The external carotid artery runs forward and out through a 

 small foramen into the orbit, passing outwards below the maxillary 

 branch of the*fifth cranial nerve to supply the muscles of the eye, 

 the upper jaw and the snout. 



The hinder parts of the body are all supplied by branches coming 

 directly from the dorsal aorta. The first noticeable one of these, 

 the sub-clavian artery, arises just in front of the fourth epibranchial 

 artery and runs outwards and backwards under the dorsal peritoneum 

 of the coelom to the pectoral girdle and fin. 



A short distance behind this arises a large median vessel, the 

 cceliac artery, which runs out into the coelom in the mesogaster just 



7\ 



FIG. 77. Lateral view of the arteries of Scylhum. 



A., auricle ; A.A., anterior extension of dorsal aorta ; A.B., afferent branchial artery ; 

 A.M., anterior mesenteric artery; B., basal region of cranium; C., cceliac artery; Ca., caudal 

 artery; C.C., common carotid artery ; C.F., carotid foramen: D.A., dorsal aorta" ; E., external 

 carotid artery; E.A., epibranchial artery; E.B., efferent branchial artery; G.C., gill cleft; 

 H., hyoidean artery; I., innominate artery; I.C., internal carotid artery; II., iliac artery; 

 L., lieno-gastric artery ; M., mandibular artery ; P.M., posterior mesentric artery ; R., renal 

 arteries ; S., spiracle ; S.C., sub-clavian artery ; S.V., sinus venosus ; V., ventricle ; V.A., 

 ventral aorta. 



dorsal to the stomach and divides into two branches ; the one 

 supplies the anterior end of the stomach and the liver, while the other 

 serves the front end of the intestine and the pancreas. 



Two further median trunks take their origin quite close together 

 about an inch and a half further back ; these are the anterior mesen- 

 teric and the lieno-gastric arteries. The former goes backwards to 

 supply the posterior part of the intestine and the gonads, and the 

 latter runs forward, thus crossing the anterior mesenteric, and is 

 distributed to the posterior bend of the stomach, the spleen and also 

 part of the pancreas. 



The next median vessel to come off from the aorta is a smaller 

 one, the posterior mesenteric artery, which runs through the meso- 

 rectum mainly to the rectal gland. Thus there are four large 

 splanchnic arteries running to the gut in the place of the large 

 coeliaco-mesenteric and small posterior mesenteric arteries present 



