THE ALIMENTARY TRA<T. 



283 



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t\vo. layers, one i/J/i longitu- 

 dinal, the other (Of) trans- 

 verse. The longitudinal layer 

 is thicker in the oesophagus, 

 and thins as it is continued to 

 the pyloric end of the stomach. 

 The circular layer, on the other 

 hand, gains in thickness ; both 

 layers are of unstriated mus- 

 cular fibre. 



(3) The submucous coat 

 (Pig. 186 A, H, and ' 17) is 

 better developed in the stomach 

 than in any other part of the 

 alimentary canal. It is formed 

 of a wide-meshed, loose con- 

 nective-tissue, which supports 

 numerous blood-vessels and 

 lymphatics. Towards the 

 mucous coat it possesses a 

 well-differentiated Jfirsen/ari* 



*a, which is arranged in 

 two layers, a longitudinal (S) 

 and a transverse (A). 



(4) The mucous coat is pos- 

 d of numerous tubular 



glands, which vary in structure 

 according to the part of the 

 membrane examined. They 

 have been the subject of much 

 investigation (Heidenhain, 

 Xussbaum, Partsch, Langley, 

 and others), and are best de- 

 scribed in three groups : those 

 of the oesophagus, of the first 

 part of the stomach, and of 

 the pyloric end of the stomach respectively ; between each pair of 

 groups are transitional forms. 



a. [The oesophageal glands are complete tubular glands lined 

 by a single layer of epithelium, which verv eloselv resemble the 



A 

 ci 

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 HB 

 M 

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The alimentary canal. 



Opening of large intestine into cloaca. 



Cloaca. 



Small intestine. 



Duodenum. 



Urinary bladder. 



Stomach. 



Spleen. 



Oesophagus. 



Pylorus. 



Large intestine (rectum). 



Junction of small and large intestine. 



