VENOUS SYSTEM 223 



Slit open one of the hepatic 'sinuses, and follow it back 

 into the corresponding lobe of the liver, noting its large size, 

 and the numerous veins opening into it. 



b. The Cuvierian sinuses are a pair of rather narrow 



tubes, forming lateral continuations of the sinus 



venosus, the line of the pericardium. marking the 



boundary between the two. Each is about a 



quarter of an inch long, and curves upwards from 



the sinus venosus round the side of the oesophagus, 



lying in a notch in the posterior border of the 



fifth hypo-branchial cartilage. Each Cuvierian 



sinus receives about the middle of its course the 



inferior 'jugular sinus, and at its dorsal end the 



great anterior and posterior cardinal sinuses. 



i. The inferior jugular sinus, which is 'of small 



size, can be traced forwards and inwards 



along the outer wall of the pericardial cavity ; 



and then forwards, close to the middle line, 



and ventral to the gill-arches. 



ii. The anterior cardinal sinus opens into the 



Cuvierian sinus by a small aperture placed 



immediately behind the fifth hypo -branchial 



cartilage, and guarded by a very perfect valve, 



the ventral flap of which is much the larger. 



From the opening the sinus extends for- 

 wards as a very wide irregular space, situated 

 immediately above the gill-arches. In front 



FIG. 38. Scyllittm canicula. Dissection of the venous system from the 

 ventral surface. The right half of the lower jaw and the right 

 lobe of the liver have been removed, as has also the alimentary 

 canal behind the ossophagus. (A. M. M.) 



A, nostril. AS, anterior cardinal sinus. B, right olfactory organ. 

 BV, subclavian vein. C, left half of lower jaw. D, fifth nerve crossing the 

 orbit. DC, ductus Cuvieri. E, right eye. F, cut edge of floor of mouth. 

 G-, first branchial cleft. H, ventricle. HS, left hepatic sinus. HV, left 

 hepatic vein. I, auricle. JV, left inferior jugular sinus. JV, opening 

 of right jugular sinus into sinus venosus. K, pericardial cavity. L, left lobe 

 of liver. LV, right lateral vein. M, oesophagus, cut across. MV, hyoidean 

 sinus. "N, kidney or metanephros. O, communication between the right and 

 left posterior cardinal sinuses. OS, orbital sinus. P, post-orbital sinus. PS,pos- 

 t terior cardinal sinus. PV, posterior cardinal vein. R.S, apertures of renal 

 veins into posterior cardinal veins. SA, aperture from sinus venosus to 

 auricle. SV, sinus venosus. 



