454 DISSECTION OF THE ABDOMEN. 



those on the left (e), the strongest, arch over the great end of the stomach, 

 and spread out on the anterior and posterior surfaces, gradually disappear- 

 ing on them. 



Fibrous coat. By removing the muscular layer over a small space, tlic 

 fibrous coat will appear as a white shining stratum of areolar tissue. This 

 coat gives strength to the stomach, and serves as a bed in which the larger 

 vessels and nerves ramify before their distribution to the mucous layer. 

 If a small opening is made in this membrane, the mucous coat will project 

 through the stomach to be distended with air. 



147. 



DIAGRAM REPRESENTING THE ARRANGEMENT OF THE MUSCULAR FIBRES OF THE STOMACH. 



Part of each of the two external coats is removed. 



a. External or longitudinal fibres. e. Oblique fibres, more numerous, on the right of 



6. Middle or circular. the cardiac orifice, and covering the great 



c. Sphincter of the pylorus. end of the stomach. 



d. Oblique fibres on the left of the cardiac 



opening. 



The mucous coat will come into view on cutting open the stomach, hut 

 the appearances now described can be recognized only in a recent stomach. 



This coat is a thickish layer, of a pale rose color soon after death in the 

 healthy condition. In the empty state of the stomach the membrane is 

 less vascular than during digestion ; and in infancy the natural redness is 

 greater than in childhood or old age. When the stomach is contracted the 

 membrane is thrown into numerous wavy ridges or rugce, which become 

 longitudinal along the great curve, towards the pylorus. 



The thickness of the mucous membrane is greatest near the pylorus ; 

 and at that spot it forms a fold, opposite the muscular ring, which assists 

 in closing the opening. If this membrane and its submucous layer are 

 removed from the pyloric part of the stomach, the ring of muscular fibres 

 (sphincter of the pylorus) will be more perfectly seen. 



Microscopic -structure of the mucous membrane. With the aid of a lens, 

 the surface of the mucous membrane, when well washed, may be seen to 

 be covered by shallow depressions or alveoli (fig. 148), which measure 

 from ^Q-^tli to jygth of an inch across. Generally hexagonal or polyjro- 

 nal in outline, the hollows become larger and more elongated towards the 

 small end of the stomach ; and near the pylorus the margins of the alveoli 

 project, and become irregular. In the bottom of each depression are the 

 apertures of minute tubes. 



