SYNOVIAL CAPSULES. 235 



abdomen and thorax, and invests the parts contained in these 

 cavities ; and Hke them it may be termed a reflected membrane. 



It is thin and very flexible, but dense and strong. 



It secretes, or effuses from its surface, a hquor, called synovia ; 

 which is particularly calculated to lubricate parts that move 

 upon each other. 



The fluid is nearly transparent : it has -the consistence of a 

 thin syrup, and is very tenacious or ropy. It mixes with cold 

 water, and, w^hen heated, becomes milky, and deposits some 

 pellicles without losing its viscidity. It appears to be composed 

 of eighty parts in one hundred of water ; above eleven parts of 

 fibrous matter ; and between four and five parts of albumen. 

 It also contains a small portion of soda, of muriate of soda, and 

 of phosphate of lime. 



There are in many of the joints masses of fat which appear 

 to project into the cavity, but are exterior to the synovial 

 membrane, and covered by it ; as the viscera in the abdomen 

 are covered by the peritoneum. 



They are generally situated so as to be pressed gently, but 

 not bruised, by the motions of the bones. 



In some joints, they appear like portions of the common 

 adipose membrane ; in others, they appear more vascular, and 

 have a number of blood-vessels spread upon them. Small 

 processes often project from their side like fringe. 



These masses have been considered as synovial glands ; but 

 they do not appear like glands ; and it is probable that the 

 synovia is secreted by the whole internal surface of the mem- 

 brane.* 



The synovial membrane, like the other parts of joints, is 

 insensible in a sound state, but extremely painful when inflamed. 

 The synovia, which is secreted, during the inflammation of this 

 membrane, has a purulent appearance. 



— For the sake of facility in description it is common among 

 anatomists, without admitting or denying the fact, to consider 



* Clopton Havers, ignorant that the synovia was derived by a sort of perspira- 

 tion from the inner surface of this membrane, supposed it to be secreted by these 

 masses of adipose matter, which are still known, in perpetuation of his mistake, 

 as Havers' "lands. — p. 



