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becoming gradually less and less marked, finally disappear. This 
arrangement is bilateral. The fibres marked IR represent some bundles 
of muscle which (shown in Fig. 14 IR) form an independent ring 
of muscle around the common bile-duct, between it and the duct of 
WIRSUNG. 
Fig. 12, Macerated 
duodenal portion of the 
common bile-duct of man. 
The relation of the com- 
mon bile-duct and the 
duct of WirsunG to the 
longitudinal muscular coat 
of the intestine is shown. 
x 5. 
At H are seen muscle fibres, which run almost entirely around 
the duct of Wırsung, but as these fibres approach that side of the 
pancreatic duct nearest the common bile-duct, they turn abruptly and 
run up on the duct of Wırsung in a longitudinal direction. They 
gradually diminish in volume as they ascend the duct. This structure 
is bilateral. See also Fig. 14 AH. 
Fig. 13 represents the structures seen upon removal of the mucous 
membrane from the intestinal wall in the region of the duodenal 
papilla. The inner circular muscular coat of the intestine is re- 
presented by CI, The first point to demand attention is the penetration 
of the inner circular 
muscular coat by the 
common bile-duct. At 
the spot of penetration, 
there is a simple se- 
paration of the muscle 
bundles of the inner 
circular muscle coat. It 
should be noted that 
the human specimen 
differs from the ar- 
rangement found in 
dog. It will be re- 
membered that in the 
latter animal, the inner 
Fig. 13, Macerated duodenal portion of the common bile-duct of man. The mucous 
membrane, muscularis mucosa and submucosa of the intestine have been removed. Rx >» 
