92 ANATOMY FOE, NUKSES. [CHAP. VIII. 



The peritoneum in the female is an exception to the rule that serous 

 membranes are perfectly closed sacs, as it has two openings by which the 

 Fallopian tubes communicate with its cavity. 



The inner surface of a serous membrane is free, smooth, and polished ; 

 the inner surface of one part is applied to the corresponding inner surface 

 of some other part, a very small quantity of fluid only being interposed 

 between the surfaces. The organs situated in a cavity lined by a serous 

 membrane, being themselves also covered by it, can thus glide easily against 

 its walls or upon each other, their motions being rendered smoother by the 

 lubricating fluid. 



