VIII 



CIRCULATORY SYSTEM (Continued) 

 CIRCULATORY SYSTEM OF HEPTANCHUS MACULATUS 





mi 



Veins 



Blood distributed by the arteries is re- 

 turned to the heart by several important 

 systems of veins. We shall consider these 

 vessels for Heptanchus maculatus in the 

 particular regions which they occupy. 



VEINS OF HEAD 



The anterior cardinal sinus {a.c.s., figs. 

 182 and 183) drains the blood from the 

 region around the eye, and as a large ves- 

 sel passes backward dorsal to the gills. At 

 the pectoral girdle it drops downward and 

 enters the duct of Cuvier. The vessel may 

 be thought of as arising from two terminal 

 vessels, the anterior cerebral and the an- 

 terior facial veins. 



The anterior cerebral vein (see fig. 182) 

 collects blood from the forward part of 

 the brain by two main branches; the ante- 

 rior lu'anch runs over the telencephalon 

 receiving numerous venules; the posterior 

 division drains the dorsal part of the dien- 

 cephalon and receives a few branches from 

 the optic lobes. The anterior facial or or- 

 bitonasal vein returns the blood from the 

 nasal region (see fig. 190, a.f.v.). Both the 

 anterior cerebral and the anterior facial 

 vessels empty into the large orbital sinus 

 (o.s.) back of the eyeball. Connecting the 

 two orbital sinuses is the interorbital vein 

 which passes through the cranium by way 

 of the interorbital canal (see fig. 47, i.o., 

 facing p. 44). 

 From the orbital sinus the anterior car- 

 dinal passes backward through the postorbital groove and, in the region of 

 the hyoidean arch, broadens out as the anterior cardinal sinus proper (a.c.s., 

 fig. 183) . In the pharyngeal region it receives certain nutrient veins (nil., figs. 



Fig. 182. Anterior cardinal sinus, Hep- 

 tanchus maculatus. (Mast Wolfsohn, 

 orig.) 



a.c.s., anterior cardinal sinus ; d.s., 

 Danielian sinus; nu., nutrient vessel; 

 O.S., orbital sinus. 



[198] 



