CHAPTER IX 

 THE MEMBRANES OF THE BODY 



THE mucous membrane is the proper lining of the 

 alimentary canal, the respiratory, the urinary, and the 

 genital organs. It is of a glandular construction, and in 

 some parts secretes mucus copiously. This membrane, 

 like the skin, has numerous openings upon its surface, 



FlG. 131. Plan of a secreting membrane (Howell). 



through which a large amount of fluid materials are re- 

 moved, as is seen in diarrhea and dysentery. The urinary 

 bladder, which is of a fibrous texture in its main con- 

 struction, has a thick mucous membrane that protects the 

 organ against irritation from the acrid substances in the 

 urine. 



The serous membranes are found on internal surfaces 

 that have no outlets, as the pleura, peritoneum, pericar- 

 dium, and the brain. These membranes serve to support, 

 in their various places and positions, the several organs 

 they invest. 



The pericardium forms a sac enclosing the heart; the 

 peritoneum invests the contents of the abdominal cavity; 

 and the pleura forms two sacs to support the lungs. They 

 all secrete a fluid for their lubrication. 



From the serous membranes a serous or watery fluid 

 is exuded, which affords a moist and smooth surface for 



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