DIGESTIVE GLANDS 273 



A simple arrangement of the ducts from the liver and gall- 

 bladder is that found in the common Dog-Fish {Scyllium canicula). 

 In this Elasmobranch a cystic duct leaves the gall-bladder, and, 

 after receiving several hepatic ducts from the lobes of the liver, 

 becomes the bile-duct and opens into the commencement of the 

 intestine. In the Myxinoids and in the Dipnoi (e.g. Proto-pterus), 

 there are but two hepatic ducts, one from each lobe of the liver ; 

 these unite and then meet the cystic duct to form the bile-duct 

 (Fig. 155, A). The niuiiber of hepatic ducts may, however, be 

 considerably increased, as, for example, in the Siluroid Amvurus} 

 where 8-10 separate ducts join the cystic duct. In a few 

 instances one of the hepatic ducts opens directly into the 

 intestine, independently of that which unites with the cystic 

 duct in forming the bile-duct. In the Dipnoi (e.g. Protoijterus)^ 

 and in some Teleostomi (e.g. LepidQsteus)f the bile-duct receives 

 the duct from the pancreas before Opening into the intestine. 



The Pancreas. — In the Cyclostomes (e.g. Petromyzon, Bcldlo- 

 stoma, Myxine) a rudimentary pancreas is apparently present, 

 but the evidence as to its identity is not wholly conclusive. A 

 well-developed pancreas occurs in Elasmobranchs, in at least one 

 of the Dipnoi, and probably in most Teleostomi.* 



In Elasmobranchs the pancreas is a compact structure, uni- 

 or bi-lobed, and entirely distinct from the liver. In Scyllium 

 canicula (Fig. 153), the bilobed gland lies in the angle between 

 the distal limb of the stomach and the adjacent portion of the 

 intestine, and from the smaller of its two lobes the duct issues 

 to pass to its intestinal aperture near the commencement of the 

 spiral vah'e. In most of the Teleostomi in which its existence 

 has hitherto been recorded, the pancreas is a singularly diffuse 

 gland ; and usually a considerable portion, or even the whole of 

 it, is embedded in the substance of the liver, its lobules accom- 

 panying the ramifications of the hepatic artery and duct, and 

 the portal vein. The pancreatic duct usually opens into the 

 intestine near the aperture of the bile duct (e.g. Amiurus) ; 

 sometimes the two ducts open on the apex of a common papilla 

 (e.g. Acipenser and Amia), or by their union form a common 



^ Macallum, reprinted from Proc. Canadian Institute, N.S. ii. 1884, p. 407. 

 ' Newton Parker, op. cit. p. 138. 



' Macallum, Journ. Anat. and Fhys. xx. 1886, p. 632. 



^ Legouis, Ann. Sci. Nat. (5), xvii. 1873, Art. 8 ; and :;vm. 1873, Art. 3. 

 Also Macallum, op. cit. p. 629. 



VOL. VII T 



