SACRO-ILIAC ARTICULATION. 
cavity of the temporal bone. The inferior synovial membrane is .. 
posed between the inferior surface of the cartilage and the condyle of the 
lower jaw ; and thus a double joint is constituted. 
The external lateral ligament is a short fasciculus of fibres, attached 
superiorly to a tubercular prominence, situate on the supero-external part 
of the squamous temporal bone, and inferiorly to the external surface of 
the condyle, and to the postero-external surface of the neck of the lower 
jaw, just below the condyle ; its fibres take a backward and downward 
course. 
The internal lateral ligament is looser and more elongated than the 
external. It extends from the inner surface of the squamous temporal 
maxillary bone, reaching down to the inner part of its angle. 
MovEMENT.—The temporo-maxillary articulation is the centre of every 
movement of the lower jaw. These are—elevation, lowering, lateral 
movement, and horizontal sliding, which motions together accomplish the 
grinding action necessary to triturate the hard grain upon which the 
horse feeds. 
THE SACRO-ILIAC ARTICULATION. 
Turs Jornt establishes the union of the posterior members with the 
spine, and is formed by the sacrum and os innominatum. It belongs to 
the arthrodial order of joints. On each of these two bones is a large and 
irregular articular surface, lined with a thick layer of cartilage, which is 
firmly united to them. The joint thus formed is strengthened by four 
ligaments, namely —1, the sacro-iliac ; 2, the superior ilio-sacral ; 3, the 
inferior ilio-sacral ; and 4, the sacro-sciatic. 
Wid, 
GHA 
Fic. 8.—PRoFriLe VIEW OF THE ILI0-SacRAL AND SACRO-ScIATIO LIGAMENTS 
A. Os ilium. H. Rim of the cotyloid cavity. 
B. Os pubis. K. K. Sacral spines. 
C. Os ischium., N. M. O. Tubercles on the antero-inferior 
D. Femur. spinous process of the ilium. 
E. Trochanter major externus. 1. 1 Superior ilio-sacral ligament. 
F. Large tubercle at the head of femur. 2. 3. 4. Sacro-sciatic ligament. 
G. Head of the femur. 
The sacro-iliac ligament is composed of large ligamentous fibres, which 
everywhere envelop the articulation, by firmly attaching themselves at 
