18 PROFESSOR D. J. CUNNINGHAM 



mucosa. These connective tissue septa present different appearances in specimens 

 which show different degrees of contraction of the muscular fasciculi. When the 

 sphincteric girdle is tightly contracted the spaces between the fasciculi become reduced, 

 and the septa are compressed and slender ; when, on the other hand, the muscle is 

 relaxed the spaces open out and the contained connective tissue is not so condensed. 

 It is necessary to mention this apparently simple and obvious matter, seeing that its 

 significance has not been fully appreciated by certain observers who have given descrip- 

 tions of pathological conditions of the pyloric canal. 



At the duodeno-pyloric junction, where the musculature of the stomach gives place 

 to the musculature of the intestine, several points of interest may be noted. The con- 

 nection between these two portions of the alimentary canal is not of so simple a 

 character as it is usually represented to be, and there is much variability in the 

 arrangement of both circular and longitudinal muscular fibres in different specimens. 

 It becomes necessary, therefore, that each specimen should be studied separately. 



Pyloric Canal of a Full-time Fastus (PL II. fig. 17 ; preparation by Mr Stiles). — The layer of circular 

 muscular fibres which forms that part of the sphincteric cylinder which corresponds to the greater curvature 

 is distinctly thicker than that on the opposite side. It rapidly and uniformly increases in thickness until 

 the duodeno-pyloric junction is reached, and here it comes to an end in such a manner that the pyloric 

 sphincteric ring on this side presents a broad, flat margin towards the duodenum. On the other side (i.e. lesser 

 curvature side) the margin presented by the pyloric sphincteric ring towards the duodenum is rounded, and as 

 the muscular layer is traced from this to the left over the pyloric canal it is seen to rapidly diminish in thick- 

 ness. There is no sudden or abrupt transition from the sphincteric cylinder to the sphincteric ring. The 

 pyloric canal is not fully contracted in this specimen. 



On both sides the circular muscular coat of the duodenum is absolutely cut off from the fasciculi of the 

 sphincteric ring by a distinct connective tissue septum. There is thus no direct continuity between the 

 circular muscular coat of the stomach and the corresponding coat of the duodenum. On the greater curva- 

 ture side of the section the circular fibres of the duodenum begin on the duodenal face of the sphincteric 

 ring in the form of three rounded or oval bundles, which are quite separate and which are quickly succeeded 

 by the closely applied fasciculi of the circular coat of the duodenum. On the opposite side (lesser curvature 

 side) the duodenal circular coat has an independent wedge-shaped commencement opposite the duodeno- 

 pyloric constriction. 



On both sides of the section a few of the superficial longitudinal fibres of the pylorus are carried over 

 the duodeno-pyloric constriction and become continuous with the longitudinal coat of the duodenum. These 

 fibres, more especially on the greater curvature side, form a very small part of this layer. A large proportion 

 of the deeper fibres, as they approach the pyloric opening, dip into the subjacent sphincteric cylinder and 

 traverse the substance of the sphincteric ring in the form of conspicuous diverging strands, many of which 

 reach the submucosa. The intermediate longitudinal fibres also dip into the sphincteric cylinder, but they 

 keep near to the surface, and run parallel to it, forming here an intimate intermixture of longitudinal and 

 circular fibres. A tolerably thick layer of this muscular feltwork is prolonged over the duodeno-pyloric 

 junction, so as to overlap the commencement of the duodenum on the superficial aspect of its proper circular 

 coat. It finally comes to an end a few millimetres beyond the pylorus by gradually passing into the proper 

 longitudinal coat of the duodenum. 



In this specimen, therefore, it will be seen : (1) that there is no continuity between the proper circular 

 coat of the duodenum and the circular coat of the pylorus ; (2) that the circular fibres which are carried 

 from the pylorus lie superficial to the circular coat of the duodenum, and on the same plane as the 

 longitudinal fibres of the duodenum, to which they gradually give place. 



Pyloric Canal of a Child (preparation by Mr Stiles). — The arrangement of the muscular tissue in this 

 specimen is very similar to that in the preceding section ; indeed, on the lesser curvature side of the pyloric 



