116 PILILOSOPHY OF ZOOLOGY. 
When bones are united by the intervention of flesh, the 
junction is termed Syssarcosis, (cvy cum cae 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 osseows 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- 
Jar 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 
joms 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. 
