152 GENERAL ANATOMY. 



become very sensible and generally, in inflammation trans- 

 mit painful impressions. 



191. All the serous membranes are the seat of the constant 

 deposition and absorption of a serous liquid in their cavity or in 

 their free and contiguous surface. The great extent of these 

 membranes, taken together, gives great importance to this dou- 

 ble function. The matter of this secretion, like all the others, is 

 brought by the vessels into the thickness of the membrane, 

 and particularly into its most vascular points, the fringed 

 prolongations: by what way the secreted matter leaves the 

 vessels and passes into the cavity, is not exactly known. Se- 

 creting glands have been supposed for all these membranes, 

 either in their vicinity or in their own thickness but no such 

 glands exist. Transudation by organic pores, has also been 

 supposed; but without exactly knowing the mode in which 

 the perspiratory secretions are performed, we know that tran- 

 sudation takes place in the dead body only, and then even 

 some time after death. The liquid is also continually absorbed 

 by the membrane, in the thickness of which it re-enters the 

 vessels. While the deposition and absorption remain in equi- 

 librium, the serous membranes are simply moistened on their 

 surfaces. The augmentation of the secretion or the diminu- 

 tion of the absorption, gives rise to an accumulation called 

 dropsy. 



The secreted liquid has local uses and general uses: locally, 

 it serves to preserve the separation between the two contiguous 

 layers of the serous membranes and to facilitate the motion 

 of the organs over one another; generally, it is probable, that 

 the nutritious matter thus alternately deposited and taken up 

 becomes more perfectly assimilated, previous to its employ- 

 ment in nourishing the organs. 



192. The action of the serous membranes, in health and 

 in disease particularly, is closely united with those of the 

 other organs. Thus, when they are diseased, the functions 

 of the organs they invest are more or less disturbed, and this 

 disturbance extends to a distance, and often to the whole or- 

 ganism; in the same way, affections of other organs particu- 

 larly those of the tegumentary membranes, of the circulating 



