STRUCTURE OP SYNOVIAL MEMBRANES. 



393 



3. Vesicular or Bur sal synovial membranes, Synovial bursce, Bur see 

 mucosce. In these the membrane has the form of a simple sac, interposed, so as to 

 prevent friction, between two surfaces which move upon each other. The synovial 

 sac in such cases is flattened and has its two opposite sides in apposition by their 

 inner surface, which is free and lubricated with synovia, whilst the outer surface is 

 attached by areolar tissue to the moving parts between which the sac is placed. 



In regard to situation, the bursae may be either deep-seated or subcutaneous. 

 The former are for the most part placed between a muscle or its tendon and a bone 

 or the exterior of a joint, less commonly between two muscles or tendons : certain 

 of the bursse situated in the neighbourhood of joints not unfrequently open into 

 them. The subcutaneous bursse lie immediately under the skin, and are found in 

 various regions of the body interposed between the skin and some firm prominence 



Fig. 450. A. RAMIFIED CONNECTIVE-TISSUE CORPUSCLES, FROM ARTICULAR SYNOVIAL MEMBRANE OF ox. 

 CHLORIDE OF GOLD PREPARATION. 250 DIAMETERS. (E. A. S. ) 



B. PORTION OF THE SURFACE OF A VAGINAL SYNOVIAL MEMBRANE, AFTER TREATMENT WITH 



NITRATE OF SILVER. 250 DIAMETERS. (E. A. S.) 



The cell-spaces of the tissue and the nuclei of the contained cells only are represented, e, epithelioid 

 arrangement of cells ; s, ramified cells. 



beneath it. The large bursa situated over the patella is a well-known example of 

 this class, but similar though smaller bursae are found also over the olecranon, the 

 malleoli, the knuckles, and various other prominent parts. It must, however, be 

 observed that, among these subcutaneous bursse, some are reckoned which do not 

 always present the characters of true synovial sacs, but look more like mere recesses 

 in the subcutaneous areolar tissue, larger and more defined than the neighbouring 

 areolse, but still not bounded by an evident synovial membrane. These may be 

 looked on as examples of less developed structure, forming a transition between the 

 areolar tissue spaces and perfect synovial cavities ; indeed it may happen that what 

 is a well developed synovial bursa in one subject is merely an enlarged areola in 

 another. Many of the bursse do not appear until after birth, and they are said to 

 increase in number as age advances. 



Structure of synovial membranes. The synovial membranes are composed 

 entirely of connective tissue with the usual cells and fibres of that tissue. It was 

 formerly stated, and is still asserted by some authors, that they are lined with an 



