STOMACH DIGESTION 67 



The peritoneum also covers the outside of all the abdominal organs. 

 Such a membrane, lining a cavity which is not in open communication 

 with the air, is a serous membrane. The peritoneum is the largest and 

 most important serous membrane. It is a thin, closely-woven network 

 of interlacing cells covered by a single layer of flat cells, which give it 

 a shiny appearance. It is moistened by a small quantity of watery fluid, 

 which is not produced by glands, but is a part of the lymphatic circu- 

 lation. Its smoothness per- 

 mits easy movements among 

 the organs of the abdomen. 



86. The stomach. The 



stomach is the first organ 

 into which the food passes 

 when it leaves the esoph- 

 agus. It lies mostly on the 

 left side of the abdomen 



. ir , . . . Organs in the upper part of the abdomen. 



half covered by the lower 



* a liver, raised up. 



ribs. It is a COnical en- b gall bladder upon the under surface of the 



largement of the alimen- c spl g r ' 



tary canal, and is situated d stomach. 



between the esophagus ' ~ 



and the small intestine. the gaii bladder. 



It is about twelve inches f f ^enum. 



in length and five inches 



in diameter. It is composed of a layer of muscle covered 



with peritoneum and lined with mucous membrane. Its 



walls are from ^ to -| inch in thickness. It is hung in 



place by a short curtain of peritoneum, which is attached 



above to the under-surface of the liver and diaphragm. 



The esophagus opens into the stomach at its upper left 



side, called the cardiac extremity. The opening into the 



intestine is at the right and narrowest part, and is called 



the pylorus. The pylorus can be closed by a thick ring of 



muscle. 



