328 THE ANATOMY OF THE HOKSB. 



into it, it is partially divided into right and left halves, or leaflets. 



Ligamenta Arcuata. — On each side of the pillars the rim of the 

 diaphragm arches with a free edge over the apices of the psoas muscles, 

 foi-ming the so-called arcuate ligament. 



Foramma of the diaphragm. 



The Foramen Sinistrum. — This is a slit between the fibres of the right 

 cms, formed slightly to the left of the mesial plane, and a little below 

 the spine. It transmits the (esophagus, the oesophageal continuations of 

 the vagus nerves, and the pleuro-cesophageal branch of the gastric artery. 



The Foramen Dextrum. — This is the aperture by which the posterior 

 vena cava passes from the abdomen to the thorax. It is formed near 

 the middle of the tendinous centre, but a little to the right of the mesial 

 plane. The margins of the opening are closely adherent to the wall of 

 the vein, and here the phrenic sinuses empty. 



The Hiatus Aorticus. — This is the opening between the right and left 

 pillars, close to the spine. It gives passage to the posterior aorta, and 

 to the initial portions of the thoracic duct and great azygos veins. 



Between the crus and the psoas parvus on each side the gangliated 

 cord of the sympathetic passes, and a little outward the great splanch- 

 nic nerve passes between the same muscle and the edge of the 

 diaphragm. The asternal vessels penetrate the edge of the diaphragm 

 at the 9th chondro-costal joint. 



Action of the Diaphragm. — The diaphragm is the principal muscle of 

 inspiration. When it contracts, it moves backwards, and thus increases 

 the antero-posterior diameter of the thorax. In this action it pushes 

 back the abdominal viscera, and causes the abdominal wall to descend. 

 The movements of the diaphragm affect principally its periphery, any 

 great backward movement of the tendinous centre being prevented by 

 the posterior vena cava, which passes like a ligament between the centre 

 and the heart. 



STRUCTURE OP THE STOMACH. 



The wall of the stomach comprises four layers, viz., serous, muscular, 

 submucous, and mucous. 



1. The Serous Coat is a smooth, glistening covering derived from the 

 eritoneum. It is united to the subjacent muscular coat by areolar 



tissue sometimes termed the subserous coat. 



2. The Muscular Coat. — This can be best displayed on &, stomach 

 which has been boiled for a few minutes. If two such stomachs can he 

 procured, one of them should be everted and moderately inflated, and 

 then its mucous coat stripped off with fingers and forceps. From the 

 other, similarly inflated, the peritoneum should be stripped off. The 

 muscular fibres are disposed in three planes, viz., an outer longi- 

 tudinal, a middle circular, and an inner oblique layer. Of these the 



