492 



ANATOMY OF VERTEBRATES. 



379 



Congested hepatic veins, liver of Squirrel, cxxn. 



liver of lower Mammals, as in that of the squirrel figured by 

 J. Miiller, 1 fig. 379, the uncongested pale peripheral portions of 



the lobules, nearest the 

 interlobular fissures, e, e, 

 may suggest an arrange- 



v Oc5 O 



ment of ultimate or ini- 

 tial biliary ducts, which 

 is merely clue to partial 

 congestion. 2 The struc- 

 ture of the liver is the 

 same throughout the 

 class ; the form of the 

 gland varies, governed 

 mainly by relations of 

 package with adjoining 

 abdominal viscera, and by the degree in which it may be affected 

 by inflections of the trunk. 



339. Pancreas of Mammalia. This conglomerate gland here 

 differs chiefly from that in birds by the progressive development 

 of a part more or less distinct from that which is lodged within 

 the loop or fold of the duodenum : such added part may be 

 represented by that freely projecting end of a fold of the bird's 

 duodenal pancreas (vol. ii. p. 175, fig. 87, q\ which stretches to- 

 wards the spleen, but there is no transverse part of the gland 

 extending at right angles from the duodenal portion, like that 

 which forms the splenic or transverse pancreas in the Mammalian 

 class, and which ultimately becomes the main part or body of the 

 gland in them. In most Mammals the pancreas is of a pale flesh 

 colour, but usually less pink or of less decided tint than in birds : 

 it is firmer in texture, and shows more plainly its conglomerate 

 structure. 



The pancreas in the Ornithorhynchus is a thin, somewhat 

 ramified gland bent upon itself; the left and larger portion de- 

 scends by the side of the left lobe of the spleen. The pancreas is 

 thicker in the Echidna, and enlarges considerably towards the 

 duodenum. The principal difference occurs in the place of ter- 

 mination of the pancreatic duct, which, in the Ornithorhynchus, 

 joins the ductus choledochus, but in the Echidna terminates sepa- 

 rately in the duodenum and nearer the pylorus than does the ductus 

 choledochus. The arrangement of the hepatic and pancreatic 

 ducts is thus conformable to the Mammalian type, and the Orni- 



1 cxxn. pi. xi. fig. 11. 



2 Well explained in CLVIII'', p. 185. 



