1008 THE DIGESTIVE SYSTEM. 
phagus. Over the great curvature and on the two surfaces they are present as an 
extremely thin and irregular sheet. Towards the pylorus the longitudinal fibres grow 
much thicker, and also much tougher and more closely united, but they do not ‘take 
any part in the formation of the py ‘lorie valve. 
A specially-condensed band of these can be often made out both on the front and back 
at the antrum pylori, the form of which is said to be due to their presence. These bands are 
known as the pyloric ligaments (liga- 
menta pylori). 
The middle layer (stratum. cir- 
culare) is composed mainly of circular 
fibres, continuous with the more 
superficial of the circular fibres at 
the lower end of the cesophagus (Fig. 
680, B). They do not commence 
as a series of circular bundles sur- 
rounding the fundus, as usually 
described. On the contrary, they 
begin as a set of U-shaped bundles 
which loop over the lesser curvature 
at the right of the cardia, and pass 
downwards and to the left on both 
surfaces. Further to the right these 
looped fibres are succeeded by circles 
which surround the organ completely. 
Traced towards the narrow end of the 
stomach, the circular bundles grow 
thicker, and at the pylorus ‘they 
undergo a further increase, giving 
rise to the pyloric sphincter whieh 
surrounds the orifice as a_ thick 
muscular ring. 
On the gastric side the pyloric 
sphincter passes gradually into the 
thick circular fibres of the pyloric 
portion of the stomach. On the 
opposite side it ceases abruptly, only 
its outer part being continued into 
the circular fibres of the duodenum 
(Fig. 681). 
The cnternal layer (fibre oblique) 
is composed of fibres which are 
arranged on the fundus and adjacent 
parts of the stomach, in much the 
same manner as those of the middle 
layer are on the body and_ pyloric 
portion of the organ (Fig. 680, C). 
Continuous above with the deeper 
circular fibres of the lower end of the 
cesophagus, they begin as U-shaped 
bundles which loop over the stomach 
Mic. .680.—THE THREE LAYERS OF THE MuscULAR Coat OF jmmediately to the left of the cardia, 
THE STOMACH, A, Outer or longitudinal layer ; B, Middle and run very obliquely downwards 
or circular layer ; C, Internal or oblique layer. «, Longi- ‘ , v ao 
tudinal fibres of esophagus ; 6, Superticial circular fibres and to the right for a considerable 
of cesophagus passing into circular fibres of stomach in B ; distance on both surfaces of the 
¢, Deep circular fibres of cesophagus passing into oblique organ. These looped fibres, as we 
fibres of stomach in C; d, Oblique fibres forming rings at pass to the left, gradually become 
the fundus ; e, Submucosa, 
less oblique, and finally form circles 
which surround the wide end of the stomach completely, even as far as the summit 
of the fundus. The oblique fibres can be most readily shown by removing the 
circular fibres on either surface below the cardia. When traced towards the right, 
they will be found to terminate by turning down and joining the fibres of the circular 
layer. 
