PLATYPUS AND ECHIDNA. 



Lesser Omentum. — Foramen of Winslow. — In the 

 Platypus there is no right margin of the lesser omentum 

 (gastro-hepatic) as in the human type. The gastro- 

 hepatic omentum is directly continuous with the meso- 

 duodenum; and this, with the duodenum which it sup- 

 ports and the portion of proximal colon related to it, can 

 be with the lesser omentum lifted in one piece, from the 

 dorsal wall — right kidney — and liver as far as the portal 

 interval. In the Echidna the duodenum is less mobile — 

 the mesoduodenum has shortened and the pancreas is 

 frequently fixed by the peritoneal adhesions to the caudate 

 lobe; but the lesser omentum is free, and so the right 

 margin becomes denned. This right margin is especially 

 defined in the human subject where the duodenum is fixed 

 dorsally. In the Platypus a big spleen and great omen- 

 tum have developed projecting to the left with the gap 

 (Foramen Winslow) in the mesogaster and upper meso- 

 duodenum on the right. The foramen is large and readily 

 admits the little finger. It is easily defined by throwing 

 the mesoduodenum — duodenum — and lesser omentum to 

 the left. In the human subject this cannot be done, so to 

 define it we pass our linger behind the right edge of the 

 lesser omentum. The foramen is limited above at the 

 portal interval — ventrally we have the mesoduodenum 

 with pancreas and lesser omentum — dorsally the fissure 

 between the lobus caudatus and spigelian lobe — and cau- 

 dally a fold from the mesoduodenum to the ventral part 

 of the inf. v. cava. 



Pancreatic Duct in Platypus. — This is traced within 

 the mesoduodenum following the curve of the duodenum, 

 and though close to the latter structure at its proximal 

 portion gradually inclines out below, and may lie 3 cm. 

 from the duodenal wall. Opposite the junction of the 

 descending and transverse portions of the duodenum it 



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