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mucous membrane was removed and with it the muscularis mucosa. 
The appearances at this stage are represented in Fig. 1. 
From the point where the common bile-duct enters the intestine 
A to the point R the muscle fibres of the inner circular muscular 
coat of the intestine are seen to pass over the common bile-duct. 
From the point R, to the point C, an irregular arrangement of muscle 
bundles is seen to exist. This arrangement resembles in shape more 
or less that of a mark of interrogation, placed in a horizontal position. 
The structure has its origin 1) partly in the fibres of the inner cir- 
cular muscular coat of the intestine, 2) partly in fibres which lie under 
the inner circular muscular coat and which arise from the median line 
of the bile-duct, and 3) partly from the ring of muscle surrounding 
the mouth of the bile-duct. The fibres after this origin run forward 
(i. e. towards the lower end of the duodenum) and, passing under the 
fibres of the inner circular muscular coat of the intestine, blend with 
the fibres of the outer longitudinal muscular coat. 
Out of eight specimens I found no two cases in which this ir- 
regular arrangement was alike. A description of the mode of origin 
and termination of these muscle bundles is accordingly of but little 
value although an exact determination was made in each case. 
Continuing from the point C to the mouth of the common bile- 
duct M, one can see muscle fibres running around the end of the 
common bile-duct. A careful examination of this region shows that 
a complete ring of muscle surrounds the mouth of the common bile- 
duct. At the same time, close observation reveals a certain number 
of muscle fibres running off from the two sides of this annulus of 
muscle. These latter are in reality part of the ring of muscle and 
after separating from the ring at its sides bend abruptly forward i. e. 
towards the lower end of the duodenum. This ring of muscle with 
the lateral muscle bundles arising from it constitutes the sphincter of 
the ductus communis choledochus. 
In Fig. 1 the muscle bundle seen coming off from the non-pan- 
creatic!) side (see X) of the annulus of muscle corresponds with the 
arrangement usually found. At first sight there seems to be no corre- 
sponding bundle for the other side (i. e. pancreatic side) of the muscle 
ring. It will be remembered, however, that the structure similar to a 
1) The terms non-pancreatic and pancreatic are used here to dis- 
criminate between the two sides of the bile-duct. The pancreatic side 
is so called because the common bile-duct is usually joined on this side 
by the duct of Wrrsune. 
