PLATYPUS AND ECHIDNA. 



(b) Echidna. — Gall Bladder. — In the Echidna this 

 is also somewhat pear-shaped, usually distended with bile, 

 and presents for examination a fundus and body. Only 

 rarely can a narrowed portion or neck be defined. It 

 lies in a fossa on the under surface of the cystic or mesial 

 lobe, and it is not usual for the fossa to reach the ventral 

 edge of the liver. In one specimen there was an interval 

 of .75 cm. of hepatic tissue between the fundus and the 

 ventral edge. It measures 3-3.5 cm. in length and later- 

 ally 2.5 cm. The fundus usually projects beyond the 

 ventral border, and is mobile, being completely invested 

 with peritoneum, the body and cystic duct being invested 

 on the ventral surface and sides onlv. Dorsallv the cystic 

 fossa narrows, forming a notch lodging the proximal half 

 of the cystic duct, which thus lies between the right and 

 left portions of the cystic lobe. The remaining half of 

 the cystic duct lies in the portal fissure or interval between 

 the inner portion of the caudate and right lateral on the 

 right side and the left lateral on the left. On the other 

 hand the fossa may extend to the coronal fissure, so that 

 the cystic duct lies wholly related to the portal interval. 



The Cystic Duct measures 1 cm. long, and at the 

 portal interval it is joined by the hepatic ducts, and 

 becomes the common bile duct. This is traced with the 

 hepatic artery on the left and the portal vein dorsallv 

 in the groove at the junction of the caudate and spigelian 

 lodes. It runs in the right extremity of the lesser omen- 

 tum (gastro-hepatic), which is more defined from the 

 mesoduodenum than in the Platypus, since the pancreas 

 is becoming more fixed and even adherent to the caudate 

 lobe. The common duct measures about 4 cm., and it is 

 joined by the pancreatic duct 2 cm. from its termination 

 in the duodenum, though in a female the distance was 

 only .75 cm. Contrary to Owen's opinion, I hav^ never 



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