BLOOD-VASCTI AK SYSTEM OF THE TILE-FISH. 



99 



small branches (33) to the membranes lining the orbit. It then curves slightly dor- 

 solateral:! and. passing between the oblique muscles of the eyeball, gives off a small 

 branch (3 ft which divides to each of these two muscles and to the mucous lining of 

 the orbit. The main trunk continues craniad and. passing through a foramen in the 

 prefrontal bone, occupies a 

 position just ventral to the 

 olfactory organ, which it sup- 

 plies by means of one or two 

 small branches (35). At this 

 point, also, a branch (36) 

 runs ventrocraniad to supply 

 the maxilla, the roof of the 

 mouth, and the maxillary 

 breathing valve (Dahlgren, 

 1898). The direct continua- 

 tion of the main artery ex- 

 tends craniad ventral to the 

 nasal bones, where it gives 

 off small branches to the 

 upper lip and membranes 

 of this region, and finally 

 pierces the premaxilla as the 

 superior dental artery (37). 



The internal carotid wr- 

 it ry and its hrii iii-Jii s (tig. IB, 

 pi. i). The internal carotid 

 artery (25) runs mesad and 

 slightly craniad until it 

 reaches the median line, then 

 dorsad for a short distance, 

 accompanied by the internal 

 carotid of the opposite side. 

 with which it anastomoses to 

 form a single median vessel, 

 the carotis interna impar 

 (!<>). The latter continues 

 dorsad, passing through a 

 median foramen in the basi- 

 sphenoid, and on the ventral 

 surface of the hypophysis 

 divides into two pairs of vessels, the anterior and posterior cerebral arteries. 



The anterior cerebral arteries run craniad, side by side, to supply the telenceph- 

 alon. The posterior vessels curve laterad and caudad over the Iobi inferiores to join 

 again in the median line on the ventral surface of the medulla near its cranial end. 

 At this point they give off anterior and posterior branches, the former supplying the 



Fig. 11. — Cranial portion of the arterial system in tin: Bounder I / imandafer- 

 ruginea). Ventral aspect, natural size. On the right side the ventral ends 

 of the efferent branchial arteries and their branches are reflected so as to 

 bring them into one plane. 



