58 



a SYNOVIAL MEMBRANES. 



A COMMON ERROR CORRECTED. 



Of three kinds of synovial membranes that exist, the articu- 

 lator)', the vagina/ and the vesicular; the two former are 

 found, one in the foot and the other in very close proximity to 

 it. The articulatory lie in loose folds around the articulatory 

 surfaces, and do not as is generally supposed cover the articulati?ig 

 surfaces. They form circumscribed sacs it is true. Their 

 edges are inserted along the margin of the articulating surfaces, 

 and their office is to secrete the synovial fluid which insinuates 

 itself between the bearing surfaces of the joint. In the coffin- 

 joint one of these membranes encloses the articulating surfaces 

 of three bones, those of the pedal and coronal bones; and the 

 upper and anterior surfaces of the navicular bone; while the 

 inferior surface of the latter bone forms a distinct articulation 

 with the portion of the perforans that glides upon or against it. 

 This latter articulation has a synovial membrane independently 

 of the one above it, and is the one nearest to the internal apex 

 of the frog, which I have strong reasons for thinking presses 

 upward but too frequently, and aggravates the contracted 

 condition of the foot. The example of a vaginal mem- 

 brane found near the foot, is that which lines the enclosed sac 

 or sheath which is formed by the perforatus for the passage of 

 the perforans, just before it reaches the navicular bone. 



DISEASES OF SYNOVIAL MEMBRANES AND THEIR SEQUELM. 



Synovial membranes are said to be non-vascular and insen- 

 sitive, except when diseased, when they become the seat of 

 intense pain. They are liable to acute and chronic inflamma- 

 tion, from concussion, blows, and strains, and mechanical inju- 

 ries, such as the puncture of a nail, broken glass, etc. They 

 may also be affected by rheumatism. Inflammatory adhesions 

 of their surfaces are found in the advanced stages of navicular 



