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circular muscle coat forms a tube-like structure which embraces the 
common bile-duct for a considerable distance. In man the common 
bile-duct plunges immediately through the muscle layer which composes 
the inner circular muscular coat. 
At S are bundles of muscle running around the common bile-duct 
(see also Fig. 14 S). These are independent rings of muscle which 
embrace the duct. Now, if we look further back on the common bile- 
duct, near the point at which it penetrates the inner circular mus- 
cular coat, we observe muscle bundles, X, which do not run entirely 
around the duct. These muscle bundles are very intimately mixed 
with the independent muscle rings which completely embrace the duct. 
The former, however, upon reaching the level of the inner circular 
muscle coat, turn abruptly forward and under the bile-duct, and after 
running for some distance toward the duodenal papilla finally end in 
the connective tissue of the submucosa of the intestine (see also 
Fig 14 X). This arrangement is bilateral. The drawing shows that 
this arrangement of muscle about the common bile-duct begins at a 
point before the duct penetrates the inner circular muscular coat. 
In this particular specimen, a muscle bundle of the inner circular 
muscular coat curves around and becomes continuous with the fibres 
marked X. It may be well to note that the fibres, X, did not termi- 
nate in all cases according to this description. In several cases these 
fibres, after turning forward and under the common bile-duct, decus- 
sated with similar ones from the opposite side and after such decussation 
became continuous with the fibres of the inner circular muscular coat 
of the intestine. In one case, the fibres, X, after turning forward sud- 
denly plunged through the inner circular muscle coat and became con- 
tinuous with the fibres of the outer longitudinal muscle coat of the 
intestine. 
Another point observed in some specimens but not in this one 
is worthy of mention. In some specimens after dissecting away the 
fibres, S, a few longitudinally and diagonally disposed fibres were seen. 
These had origin in those fibres of the outer longitudinal and inner 
circular muscle coat which lie over the common bile-duct when viewed 
as in Fig. 13. Finally in Fig. 13 a bundle of muscle fibres, X, can 
be seen on each side of the common bile-duct running parallel with 
it. These bundles arise on the surface of the common bile-duct 
(Fig. 14 K) and are covered by the fibres, F, of Fig. 12. In this 
case they run forward from under the inner circular muscular coat, 
Fig. 13 K, and bend around beneath the common bile-duct, becoming 
continuous with each other, thus forming a loop around the duct of 
14* 
