116 PHILOSOPHY OF ZOOLOGY. 



When bones are united by the intervention of flesh, the 

 junction is termed Syssarcosis, (<n cum r*$ caro.) Of this 

 sort is the union of the scapula with the ribs. In some 

 cases, particularly in the junction of the upper mandible 

 with the head, in many birds, there is an intervening thin 

 bony plate, which being flexible, admits of a small degree 

 of motion, and thus constitutes an example of osseous am- 

 phiarthrosis, 



2. Articulation by Diarthrosis presents several varie- 

 ties differing in the forms of the articular surfaces, and the 

 kind of motion of which they are susceptible. The articu- 

 lar surfaces are enveloped with cartilage, remarkable for the 

 smoothness of its free surface, and its intimate union with 

 the bone, of which it forms a protecting covering. The 

 periosteum is not continued over the surface of the carti- 

 lage, but is prolonged like a sheath over the joint, until it 

 joins that of the opposite bone. It thus forms a close bag 

 at the joint, into which nothing from without can enter, and 

 from which nothing can escape. Into this bag the lubrica- 

 ting liquor termed synovia is conveyed. It is secreted 

 by a mucous membrane on the interior, on which, as it in 

 some cases appears like little bags, the term bursa mucosa 

 has been bestowed upon it. 



The nature of synovia has never been investigated with 

 much care or success ; even the experiments which have 

 been detailed, afford results so very different, that no accu- 

 rate conclusions can be drawn from them, although the sy- 

 novia of the joints of oxen has been exclusively employed. 

 The two following analyses may here be exhibited. 



