230 THE ARTICULATIONS OF THE HORSE 
The joint capsule is very close fitting, and is attached around the margins of 
the articular surfaces. It is reinforced by the ventral sacro-iliac ligament (Lig. 
sacro-iliacum ventrale), which surrounds the joint; this is exceedingly strong above, 
where it occupies the angle between the ilium and the wing of the sacrum; it con- 
sists chiefly of nearly vertical fibers. A> 
The movements are inappreciable in the adult 
the chief desideratum. 
stability, not mobility, being 
LIGAMENTS OF THE PELVIC GIRDLE 
The following ligaments (Ligg. cinguli extremitatis pelvine) may be regarded 
as accessory to the sacro-iliac joint, although not directly connected with it: 
Fic. 244.—Petvic LigAMEeNTS AND Hip Jornt. 
1, Dorsal sacro-iliac ligament; 2, lateral sacro-iliac ligament; 3, sacro-scietic ligament; 4, greater sciatic foramen; 
5, lesser sciatic foramen; 4, line of attachment of intermuscular septum between biceps femoris and semitendinosus; 
7, capsule of hip joint; 8, capsularis muscle; 9, lateral tendon of origin of rectus femoris; 10, tuber sacrale; 11, tuber 
cox; 12, shaft of ilium; 13, superior ischiatic spine; 14, pubis; 15, tuber ischii; 16, trochanter major; 17, semimem- 
branosus; 18, fifth lumbar spine; 1/9, 20, first and second coceygeal vertebre. 
The dorsal sacro-iliac ligament (Lig. sacro-iliacum dorsale breve) is a strong 
band which is attached to the tuber sacrale and the summits of the sacral spines. 
The lateral sacro-iliac ligament (Lig. sacro-iliacum dorsale longum) is a tri- 
angular, thick sheet which is attached in front to the tuber sacrale and adjacent 
part of the medial border of the ilium above the great sciatic notch, and below to 
the lateral border of the sacrum. It blends above with the dorsal sacro-iliac liga- 
ment, below with the sacro-sciatic ligament, and behind with the coceygeal fascia. 
The sacro-sciatic ligament (Lig. sacroischiadicum s. sacrospinosum et tuber- 
osum) is an extensive quadrilateral sheet which completes the lateral pelvic wall. 
