82 THE SEROUS TISSUE. 



obtain a covering by protruding into or pushing this 

 membrane before them into its cavity. 



The structure of the serous tissue consists of thin, white, 

 transparent membranes, composed, according to Muller, of 

 fibres, like the cellular tissue, collected into bundles, and 

 forming a membrane. It has two surfaces, the one at- 

 tached, the other free. The free surface is smooth, pol- 

 ished, and constantly lubricated by an albuminous fluid, 

 which thus allows the free motion of the several organs 

 upon each other; and the microscope shows that this free 

 surface is covered by an epithelium, formed of flattened 

 scale-like cells, as the epidermis polygonal or tesselated, 

 and having each a nucleus in its centre. Some of these 

 cells are seen to elongate into hair-like filaments called 

 cilia, which are in constant vibration, and, as supposed, 

 intended to prevent stagnation of the fluids with which 

 they are in contact. 



The Synovia! Membranes are simply serous sacs of smaller 

 size found about the different joints. They line the in- 

 ternal surface of the capsular ligaments, and are thence 

 reflected upon the cartilages covering the articular ends of 

 the bones. They are also seen under the annular liga- 

 ments, around tendons and beneath fasciae. The synovial 

 fluid differs from the serous in being more viscid. 



The Bursce Mucosce forms the third division of the serous 

 system, and are also modifications of the cellular tissue. 

 They consist of serous sacs, most generally placed between 

 muscles and tendons and bones, and in connection with 

 articular cavities and ligaments. They secrete a fluid 

 for lubricating the parts with which they are in contact. 

 Mr. Hooper enumerates the following: The head has 4; 

 the shoulder joint 11; elbow joint 4; wrist and hands 15; 

 hip joint 12; knee joint 6; the foot 10 making 62 bur- 

 see mucosse to the whole body, besides others more irregular 

 in their distribution. 



The functions of the serous tissue are those of secre- 

 tion, exhalation, and absorption. The fluid secreted is 

 designed to allow free and easy motion among the several 



