CHAP. VI.] SEROUS MEMBRANES. 129 



scrotum. These are all closed at every point; so that their secretion, 

 if morbidly increased, is retained within the cavity, and can only be 

 removed by absorption, or by an opening through the membrane. 

 In the healthy state, the surfaces are only moistened; and, when 

 more fluid exists, it is the product of disease, or of post-mortem 

 change. If the surfaces be dry, or a viscid adherent matter be 

 effused upon them, the movements of the contained organ become 

 impeded, and are accompanied by a peculiar sound of friction, and 

 a vibration sensible to the hand ; both of which are well known 

 to physicians in the pericardium, pleura, and peritoneum, and may 

 frequently be noticed by the patients themselves. 



The peritoneum of the female affords a remarkable exception to 

 the closed character of serous sacs. At two points this membrane 

 is open, where it communicates with the canal of each Fallopian 

 tube at its dilated extremity. 



The blood-vessels of serous membranes are distributed in consi- 

 derable numbers in the areolar tissue which is connected with their 

 attached surface. We infer that nerves exist freely in the same 

 tissue, from the intense pain which accompanies inflammation of 

 these membranes. There is good reason to believe that lymphatics 

 also are freely distributed in their areolar tissue. 



The serous membranes connect the viscera contained in the 

 cavities to which they respectively belong, by the folds they form 

 as they pass from each viscus to the wall of the cavity. As the 

 viscera in the abdomen are so many, and the folds proportionately 

 numerous, the peritoneum is more com- Fig M 



plicated in its disposition than any other 

 serous membrane ; and it is part of the 

 study of the descriptive anatomist to shew, 

 that the remarkable complication of folds 

 which this membrane exhibits is not in- 

 consistent with its adherence to the chief 

 morphological character of serous mem- 

 branes. 



Microscopic Characters of Synovial and 

 Serous Membranes. These membranes ap- 

 pear to be essentially alike in their mi- 

 nute structure. On their free surface is a 



Single layer Of epithelium, the particles Epithelium of serous membrane :- 



of which are polygonal in shape, and of 

 transparent texture. A small fragment 

 of this pavement, from the peritoneum ^ 



VOL. I. K 



