564 



COMPARATIVE ANATOMY. 



and othei' processes, wliile tliey give rise to tlie bile-ducts by tbe 

 formation of intercellular passages, wliicb run in the axes of _ tlie 

 epitbelial chords. The hepatic lobes, which are formed on_ either 

 side, fuse with one another into a single organ. The two primitive 

 diverticula, after they have formed the bile-ducts in the parenchyma 

 of the liver, and have been continued iuto the network of cellular 

 chords, form the efferent ducts of the liver. 



The liver, which is thus differentiated from the enteron, forms 

 a compact, and ordinarily, very large organ ; it is embedded in a 

 fold of the peritoneum, which extends from the anterior portion of 

 the enteric tube to the anterior wall of the abdomen. 



In Fishes, the liver generally forms a single, undivided mass, but 

 sometimes it consists of two, or more lobes. There are two large 



portions in the Amphibia ; it is gene- 

 rally simple in the Ophidii, and is 

 merely notched at the margin in the 

 Saurii ; in the Crocodilini and Chelonii 

 it is again divided into two lobes, 

 which in the latter are widely sepa- 

 rated from one another, and united 

 by a slender transverse bridge. Ordi- 

 narily two lobes are, sometimes more, 

 sometimes less, indicated in the Mam- 

 malia. In the Carnivora, Rodeutia, 

 some Marsupialia, Simile, and others 

 we find, indeed, multilobate forms, but 

 these may be referred to two larger 

 primary lobes. 



There are various modifications in 

 the character of the efferent ducts 

 (ductus hepato-enterici) in relation to 

 their primitively double character ; for 

 either the first condition persists, or 

 the two ducts are gi'adually fused to- 

 gether, that is to say, the diverticulum 

 of the enteron is converted into a 

 single duct, or, lastly, the primitive 

 ducts are atrophied, and secondary 

 canals are converted into efferent 

 ducts ; in this case there is a large 

 number of ducts (in the Saurii and 

 Ophidii). A unilatei-al C96cal diverti- 

 culum, the gall-bladder (Fig. 320,/) 

 is placed on these ducts; it has very 

 various relations, and is by no means 

 a constant structure. 



The pancreas is developed in the 

 same way as the liver — from a diverticulum of the wall of the 

 enteron, which is developed behind the rudiment of the liver. The 



Fig. 320. Enteric canal of Ardea 

 cinerea. i ffisophagus and crop. 

 pv Proventriculus. v Gizzard. 

 v' Antrum pylori. d Duodenal 

 loop, it Mid-gut. h Hind-gut. 

 c Part of the single cseoum. 

 cl Cloaca and Bursa Fabricii. 

 h Liver, dh Ductus hcpato-en- 

 tericus. /Gall-bladder, p Pancreas. 

 dp Pancreatic duct. 



