16 PROFESSOR D. J. CUNNINGHAM 



and almost suggests a slight degree of telescoping of the one into the other.* In the 

 cadaver which has been properly prepared by formalin injection, the pyloric opening is 

 almost invariably found tightly closed — no matter what the condition of the pyloric 

 canal may be. It is only on very rare occasions that the opening is patent. In such 

 cases it is circular, surrounded by the ring-like ledge which has been called the pyloric 

 valve, and may be large enough to admit the point of the little finger ; but this is not 

 a natural condition. It is safe to conclude that during life the pyloric opening at the 

 extremity of the pyloric canal is always rigidly closed, except during digestion, when it. 

 opens intermittently and at irregular intervals (Hirsch (20) and Cannon (6)) to allow 

 the passage of material from the stomach to the duodenum.! 



The musculature of the pyloric canal constitutes, as Muller (40) has pointed out, 

 one of the leading peculiarities of this section of the stomach. Both the longitudinal 

 and the circular fasciculi are present in greater mass than in any other part of the 

 organ. The circular fibres are disposed in the form of a thick sphincteric muscular 

 cylinder which surrounds the entire length of the canal (PL II. figs. 15 and 17 ; see 

 also PI. IV. fig. 40). At the duodeno-pyloric constriction the margin of this cylinder 

 becomes increased in thickness, forming thereby the massive muscular ring which 

 encircles the pyloric opening and constitutes the pyloric sphincteric ring. The knob- 

 like appearance presented by the extremity of the pyloric canal when viewed from the 

 interior of the duodenum is produced by the presence, beneath the mucosa, of this 

 muscular ring. The sphincteric cylinder which surrounds the pyloric canal varies 

 much in its thickness in accordance with different degrees of contraction of the canal. 

 In the firmly contracted condition, and when in consequence the canal is tightly closed, 

 the muscle-layer is very nearly equally thick throughout its whole length. This is 

 more especially the case on the side of the greater curvature where the circular muscular 

 fibres turn over the sulcus intermedius before they finally thin down (PL II. figs. 15 

 and 16) and gradually become uniform in thickness with the circular fibres of the 

 pyloric vestibule. On the lesser curvature side of the canal the transition is, as a 

 rule, less abrupt, and a gradual diminution in thickness takes place as this layer is 

 traced from the sphincteric ring towards the pyloric vestibule. It would appear, 

 therefore, that the sphincteric cylinder on this side is rather weaker (or perhaps less 

 firmly contracted) than on the greater curvature side — a circumstance which may be 

 due to the close apposition of this aspect of the pyloric canal with the liver. 



The longitudinal muscle-fibres likewise form a thick layer on the superficial aspect 

 of the sphincteric cylinder and ring. They are uniformly disposed around the pyloric 

 canal, but as a rule comparatively few of these fibres pass superficially over the duodeno- 



* The projection of the extremity of the pyloric canal into the commencement of the duodenum has been stated 

 by various observers to be one of the signs of pyloric stenosis in the infant (Pflaundler, p. 75 (41)). In all 

 probability the condition is more pronounced in these eases. 



t The passage of bile into the stomach shows that under certain conditions incontinence of the pyloric opening 

 may take place. As might be expected, bile flows more readily into the empty than into the full stomach 

 (Kcjssmaul, p. 1651 (29)). 



