STRUCTURE OF STOMACH. 



455 



By means of a thin section under the microscope the membrane may 

 be observed to be composed almost altogether of minute vertical tubes, 

 which lie side by side, and project into the submucous tissue. Measuring 

 from ^th to gV^ of an inch in length, the tubes are closed at. the deep 

 end ; but they open on the surface of the stomach both in the alveoli (fig. 

 148) and in the interalveolar spaces. They are formed of a homogeneous 

 membrane, and are for the most part straight, but towards the pylorus 

 they increase in length, and are somewhat sacculated at the deep extrem- 

 ity; some are divided into two or more pieces (fig. 149). 



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Fig. 148. 



Fig. 149. 



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 : O 



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CD 



ALVEOLAR DEPRESSIONS op THE 

 Mucous MKMBRAXR OF THB STO- 

 MACH, magnified 32 diameters, 

 with the minute tubes opening 

 into them (Sprott Boyd.) 



ENLARGED REPRESENTATION OF THE TUBES OF THE 

 STOMACH. 



a. Gastric tube from the pyloric end lined, throughout, 



by columnar epithelium (Kfilliker). 



b. Gastric tube from the cardiac end, with a columnar 



epithelium lining near the mouth, and flattened nu- 

 cleated granular cells beyond (Thomson). 



At the cardiac end of the stomach the tubes are lined at the free end 

 by columnar epithelium (fig. 149, b) ; but in the closed end by flattened 

 and granular nucleated cells, which are named peptic glands, and are sup- 

 posed to give origin to the gastric fluid. Towards the pylorus the tubes 

 are closed throughout by columnar epithelium (fig. 149, a) and secrete 

 mucus. 



A columnar epithelium covers the surface of the mucous membrane, and 

 enters the small tubules. 



On the attached surface of the mucous membrane is a thin layer of in- 

 voluntary muscular fibres, separating it from the fibrous coat : it is said to 

 send offsets amongst the tubules. 



Bloodvessels. The arteries of the stomach, after supplying the mus- 

 cular coat, ramify in the submucous tissue ; from this anastomosis fine 

 offsets are continued on the tubes to the inner surface of the mucous mem- 

 brane, where they form a network. The veins begin in the mucous mem- 

 brane, receive branches from the muscular coat, and deliver their blood 

 into the portal system. 



Lymphatics. Two layers of absorbents, superficial and deep, exist in 

 the stomach : the latter begin in a plexus beneath the tubules, and form a 



