213 
in the submucosa of the intestinal wall. The large opening — to 
the right — is the lumen of the ductus communis choledochus; the 
narrow slit — to the left — represents the collapsed lumen of the 
duct of Wırsung. At the point X, muscle bundles cut in cross 
section and sometimes diagonally are seen. These bundles represent 
those fibres of the sphincter muscle which do not run entirely around 
the common bile-duct. They become detached at the side of the duct 
from the sphincter proper and turn forward. These bundles then run 
forward, under the common bile-duct and gradually approach the 
bundles of the opposite side; they finally end free in the connective 
tissue of the submucosa near the orifice of the common bile-duct. 
These bundles correspond to the fibres, X, of the macerated specimen. 
It is probable that the fibres, K, of the macerated specimen are also 
included among the bundles described above, but we have not been 
able to distinguish them in the sections from the others. 
The remaining bundles of muscle about the common bile-duct 
belong to the sphincter muscle proper: they correspond to the fibres, S, 
of the macerated specimen. A bundle of muscle fibres cut longitudi- 
nally is seen running between the lumen of the duct of Wırsung and 
that of the common bile-duct. I consider this to be a bundle of the 
sphincter muscle and belive that it corresponds to the “double sphincter” 
arrangement found in the dog and rabbit, and described above. 
N 
N 
K 
Fig. 16. Cross-section at the entrance of the common bile-duct into the intestinal 
wall of man. X 30. 
The second section (Fig. 16) represents the common bile-duct 
just before it has penetrated the muscle coats of the intestine. Around 
the common bile-duct, are seen muscle bundles cut transversely. These 
represent the fibres, K, of the macerated specimen. No muscle fibres 
