SYNOVIAL MEMBRANES AND SYNOVIA. 315 



titious ; while others, like most of the digestive fluids, are produced at certain 

 intervals and are taken up again by the blood. 



TABULAB VIEW OF THE SECRETED FLUIDS. 

 Secretions Proper. 



Synovia. 



Mucus, in many varieties. 



Sebaceous matter. 



Cerumen, the waxy secretion of the external 



auditory meatus. 

 Meibomian fluid. 

 Milk and colostrum. 

 Tears. 



Saliva. 



Gastric juice. 

 Pancreatic juice. 



Secretion of the glands of B runner. 

 Secretion of the follicles of Lieberkiihn. 

 Secretion of the follicles of the large intes- 

 tine. 

 Bile (also an excretion). 



Excretions. 

 Perspiration and the secretion of the axillary j Urine. 



glands. I Bile (also a secretion). 



Fluids containing Formed Anatomical Elements. 

 Seminal fluid, containing, in addition to spermatozoids, the secretions of a number of 



glandular structures. 

 Fluid of the Graafian follicles. 



The serous cavities are now regarded as sacs connected with the lym- 

 phatic system, and the liquids of these cavities are not classed with the secre- 

 tions. 



Synovial Membranes and Synovia. The true synovial membranes are 

 found in the diarthrodial, or movable articulations ; but in various parts of 

 the body are found closed sacs, sheaths etc., which resemble synovial mem- 

 branes both in structure and in their office. Every movable joint is envel- 

 oped in a capsule, which is closely adherent to the edges of the articular 

 cartilage and is even reflected upon its surface for a short distance ; but it is 

 now the general opinion that the cartilage which incrusts the articulating 

 extremities of the bones, though bathed in synovial fluid, is not itself cov- 

 ered by a distinct membrane. 



The fibrous portion of the synovial membranes is dense and resisting. It 

 is composed of ordinary fibrous tissue, with a few elastic fibres, and blood- 

 vessels. The internal surface is lined with small cells of flattened endothe- 

 lium with rather large, rounded nuclei. These cells exist in one, two, three 

 or sometimes four layers. 



In most of the joints, especially those of large size, as the knee and the 

 hip, the synovial membrane is thrown into folds which contain adipose tis- 

 sue. In nearly all the joints, the membrane presents fringed, vascular pro- 

 cesses, called synovial fringes. These are composed of looped vessels of con- 

 siderable size ; and when injected they bear a certain resemblance to the 

 choroid plexus. The edges of these fringes present a number of leaf-like, 

 membranous appendages, of a great variety of curious forms. They are gen- 

 erally situated near the attachment of the membrane to the cartilage. 



The arrangement of the synovial bursae is very simple. Wherever a ten- 

 don plays over a bony surface, there is a delicate membrane in the form of 



