THE STOMACH 417 
The use of the term ligament in regard to the arrangement here is somewhat misleading, 
since the stomach is attached to the crus of the diaphragm by areolar tissue; the peritoneum 
passes from the diaphragm to the stomach on each side of the area of adhesion. In soft material 
there is the appearance of a ligament composed of two layers of peritoneum, but this is an artefact. 
2. The lesser omentum (Omentum minus) connects the lesser curvature and 
the first part of the duodenum with the liver below the cesophageal notch and the 
portal fissure. 
The part of the omentum which extends from the liver to the stomach is designated the lig. 
hepato-gastricum, and the remainder which goes to the duodenum as the lig. hepato-duodenale. 
3. The gastro-splenic omentum (Lig. gastrolienale) passes from the left part 
of the greater curvature to the hilus of the spleen; it is continuous ventrally with 
the greater omentum. 
4. The greater omentum (Omentum majus) connects the ventral part of the 
greater curvature and the first curve of the duodenum with the terminal part of the 
great colon and the initial part of the small colon. It does not pass directly between 
these parts but forms a large sac, which will be described later. 
5. The gastro-pancreatic fold (Plica gastropancreatica) extends from the left 
sac above the cardia to the duodenum. It is attached dorsally to the liver and 
vena cava, ventrally to the pancreas. 
The stomach of the equide is relatively small, its capacity varying from two 
to four gallons (ca. 8 to 15 liters). 
The size, form, and position of the stomach are subject to considerable variation. When 
the stomach is nearly empty, the saccus cxcus contains only gas and is strongly contracted; the 
middle part (physiological fundus) contains the ingesta and preserves its rounded character, 
while the pyloric part is contracted. In this state coils of small intestine usually lie ventral to the 
stomach and may separate it entirely from the colon. In exceptional cases, when the organ is 
empty and contracted, even the pyloric end is to the left of the median plane. When distended, 
the middle part settles down some four or five inches, pushing back coils of the small intestine 
which may lie between the greater curvature and the large colon, and also pushing to one side the left 
dorsal part of the great colon; the spleen, small colon, and-small intestine are pushed back by the 
distention of the left sac. When the stomach is moderately full, its most ventral part lies opposite 
to the ninth intercostal space and tenth rib, about a handbreadth above the level of the left costal 
arch. 
Structure.—The wall is composed of four coats—serous, muscular, submucous, 
and mucous. The serous coat (Tunica serosa) covers the greater part of the organ 
and is closely adherent to the muscular coat except at the curvatures. It partially 
bridges over the lesser curvature, and covers here elastic tissue which assists in 
retaining the bent form of the stomach. The peritoneal folds have been described. 
The muscular coat (Tunica muscularis) consists of three incomplete layers, an 
external of longitudinal, a middle of circular, and an internal of oblique fibers. The 
layer of longitudinal fibers (Stratum longitudinale) is very thin and exists only 
along the curvatures and at the antrum. It is not present on the saccus cxcus, 
and about the middle of the greater curvature it is almost entirely replaced by 
elastic fibers to the antrum pylori. At the lesser curvature it is continuous with the 
longitudinal fibers of the cesophagus. On the antrum pylori it forms a well-de- 
veloped complete layer which is separate from that of the curvatures. The layer 
of circular fibers (Stratum circulare) exists only on the glandular part. At the 
pyloric orifice it forms a thick ring—the pyloric sphincter (Sphincter pylori). 
Another ring, the antral sphincter, is found at the left end of the antrum pylori. 
The oblique fibers (Fibre oblique) are arranged in coarse bundles in two layers. 
The external stratum covers the left sac and is largely a continuation of the longi- 
tudinal fibers of the cesophagus. The internal stratum is found also on the left 
sac; it is continuous with the circular fibers of the cesophagus and stomach and 
exchanges fibers with the external oblique layer. It forms a remarkable loop 
around the cardiac orifice, constituting a powerful cardiac sphincter (Sphincter 
cardize). The submucous coat (Tela submucosa) is a layer of loose connective 
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