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PROCEEDINGS OF THE ANATOMICAL AND ANTHROPOLOGICAL 



gut becomes the pharynx, oesophagus, stomach, and that part of thr 

 duodenum situated in front of the opening of the common bile duct, 

 that is to say, he appears to regard the liver as a mid-gut develop- 

 ment. With this I entirely agree, inasmuch as in both these cases 

 there is but one common bile duct which opens into the intermediate 

 portion of the single duodenal tube. Thus the liver is proved to be 



Fig. 3. Diagram to illustrate evolution of single duodenum and jejunum from one yolk-sac 

 common to both embryos. Fore- and hind-guts shaded, mid-gut dotted. The ducts of the 

 pancreas Wirsung and Santorini are also seen. 



a single structure common to both twins and not two liver buds 

 fused together, and as an additional argument in support of this view 

 it may be stated that each liver has but one Spigelian lobe. For these 

 various reasons I am, therefore, of opinion that these cases prove the 

 liver to be a mid-gut development, and that Keith is perfectly correct 



