ON THE STOMACH IN MAN AND THE ANTHROPOID APE. 19 



canal and duodenum it is in every respect identical. On the greater curvature side, however, there are 

 some points of difference. The sphincteric ring of the pylorus and the circular muscular layer of the 

 duodenum are arranged in precisely the same way. The difference consists in the manner in which the 

 pyloric longitudinal and circular fibres are prolonged on to the duodenum. At the duodeno-pyloric con- 

 striction they form a feltwork, but beyond this the circular fibres free themselves from the longitudinal 

 fibres and are continued for a short distance on the duodenum as a distinct layer on the superficial aspect 

 of the longitudinal fibres. It thus happens that on this side the first part of the wall of the duodenum 

 exhibits three muscular layers, viz., from without inwards — 



(a) circular ) , , ,. , 



(b) longitudinal \ P rolon 8 ed from Py loras - 



(c) circular the proper duodenal coat. 



Very soon the superficial circular fibres disappear and the longitudinal fibres come to the surface. 



Pyloric Canal of a Child (preparation by Mr Stiles). — In this specimen only the greater curvature 

 side of the pyloric canal and the adjoining portion of the duodenum are shown. The proper circular coat 

 of the duodenum does not begin at the sphincteric ring, but at some little distance from it, so that there is 

 a complete break between the circular coats of the stomach and the intestine. Further, no superficial 

 longitudinal fibres are carried from pylorus to duodenum. A thick layer of circular fasciculi continuous 

 with the superficial part of the sphincteric ring is carried on to the duodenal wall, and this constitutes the 

 only muscular covering for a short piece of the initial part of the duodenum. After it has proceeded for 

 a short distance, it is gradually replaced by the proper longitudinal coat of the duodenum. 



Pyloric Canal of a Child (PI. II. fig. 18). — In this specimen the arrangement of the muscular fibres is 

 more simple. On both sides a certain proportion of the more superficial of the longitudinal fibres are 

 carried continuously from the pylorus on to the duodenum, but the layer which they form is much thicker 

 on the greater curvature side, and here they are very wavy. The circular muscular coat of the duodenum 

 is quite distinct from the sphincteric ring of the pylorus. On the lesser curvature side it is separated from 

 it by an interval of a few millimetres ; on the opposite side the circular fasciculi of the duodenum begin 

 close to the sphincteric ring, but are separated from it by a very evident partition of connective tissue. At 

 the pyloric constriction certain of the longitudinal fibres and the superficial circular fibres become interwoven 

 together, and with these there is a considerable admixture of connective tissue. 



A study, therefore, of these specimens (the majority of which, it will be seen, were 

 prepared by my colleague, Mr H. Stiles) brings out the following points : — 



1. The greater proportion of the pyloric longitudinal muscular fibres do not pass on 

 to the duodenum. They turn into the sphincteric ring and there spread out in the 

 form of diverging fasciculi, many of which reach the subjacent submucosa. 



2. In only one specimen did the whole of the longitudinal fibres of the pylorus pass 

 into the sphincteric ring ; and in this case the superficial circular fasciculi of the pyloric 

 sphincteric ring were carried beyond the duodeno-pyloric constriction so as to form, for 

 a short distance on the duodenum, a layer which gradually gave place to its proper 

 longitudinal coat. 



3. In all the other sections the more superficial of the pyloric longitudinal fibres 

 are continued from the stomach on to the duodenum, but the manner in which 

 they are disposed in the region of the duodeno-pyloric junction differs in different 

 individuals. 



4. The more usual way is for certain of the pyloric longitudinal fibres to proceed 

 uninterruptedly from stomach to intestine, whilst the more deeply placed fibres form an 

 interlacement with the superficial circular fibres of the sphincteric ring, and the feltwork 

 which results is then carried as a distinct layer for a short distance on to the duodenum. 



