ON THE STOMACH IN MAN AND THE ANTHROPOID APE. 17 



pyloric constriction and become continuous with the corresponding fibres of the 

 duodenum. As they approach the duodenum the deeper longitudinal fibres leave the 

 surface and, in the form of distinct fasciculi, penetrate the substance of the pyloric 

 sphincteric ring, amidst the bundles of which they end — many, however, reaching its 

 deep aspect (PI. II. figs. 15 and 16). It is not necessary to submit sections of the 

 pyloric canal to microscopic examination to see these fasciculi. They can be observed 

 by the naked eye, or at least with the aid of a magnifying glass, in most sections through 

 this region, and in no specimens in my possession are they so strongly marked as in 

 the stomach of the chimpanzee (fig. 15). This does not seem to be due to a greater 

 development of these fibres in this animal, but to the coarser character of the pene- 

 trating fasciculi. 



There can be no question that by this arrangement of the pyloric longitudinal fibres 

 in relation to the underlying circular fibres an effective apparatus, antagonistic to the 

 sphincteric ring, is provided, by means of which, when the sphincter relaxes, the pyloric 

 orifice may be dilated. Luschka, who was apparently not aware of the penetration of 

 the sphincteric ring by the longitudinal fibres, was nevertheless of the opinion that the 

 longitudinal fibres were dilators of the pylorus — a view which is endorsed by the 

 physiologist. In the article on ' Digestion ' in Schafer's Text-booh of Physiology, 

 Starling (49) remarks : " A partial relaxation of this opening (pyloric opening) is 

 brought about, partly by inhibition of the circular sphincter pylori, partly by con- 

 traction of the longitudinal fibres." 



RiiDiNGBR has given an account of the arrangement of the muscular fibres of the pylorus ("Ueber die 

 Muskelanordnung im Pfbrtner des Magens und Anus," Allg. Wien. Med. Ztcj., 1879, xxiv. 2. 9), but I 

 regret to say that I have not been able to obtain his paper. Jonnesco (27 ; p. 223), who refers to Rudinger 

 in liis description of the structure of the pylorus, remarks : " In effect the longitudinal fibres take part in 

 the formation of the pyloric sphincter by interlacing with the circular fibres : there is thus a constrictor 

 and a dilator of the pylorus." 



The description which is given by Luschka (30) (1863) and Brinton (4) (1864) of 

 the longitudinal fibres of the stomach is not generally adopted by British anatomists, 

 and yet anyone who looks into the matter can have little difficulty in satisfying himself 

 as to its general accuracy. According to these authors, the longitudinal fibres of the 

 oesophagus radiate over the stomach in all directions, but more particularly along the 

 lesser curvature, and they disappear (with the exception, perhaps, of some on the lesser 

 curvature) before they reach the pyloric part of the organ. On the body of the stomach 

 a new and independent set of longitudinal muscle-fibres take origin, and these form a 

 layer which gradually gains strength as it sweeps onwards towards the pylorus. These 

 are the fibres which for the most part come to an end by dipping in to mix with the 

 circular fasciculi of the sphincteric pyloric ring. 



When longitudinal sections through the pyloric canal, in the plane of the two 

 curvatures of the stomach, are prepared for microscopical examination, the sphincteric 

 cylinder and ring are seen to be broken up into fasciculi of different sizes by strands 

 of connective tissue which enter the muscular tissue on its deep aspect from the sub- 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART I. (NO. 2). 3 



