190 THE ARTICULATIONS OF THE HORSE 



phalanx and are here partly blended with the lateral ligaments of the pastern joint. 

 They are directed obliquely downward and backward, and end chiefly on the 

 ends and proximal border of the third sesamoid, but detach a branch to the inner 

 surface of each lateral cartilage and wing of the third phalanx. 



The inferior navicular ligament (Ligamentum phalangeo-sesamoideum) rein- 

 forces the capsule inferiorly. It is a strong layer of fibers which extend from the 

 distal border of the third sesamoid to the tendon surface of the third phalanx, 

 near the posterior margin of the articular surface. 



Movements. — The chief movements are flexion and extension. In the stand- 

 ing position the joint is extended. During volar flexion a very small amount of 

 lateral movement and rotation can be produced by manipulation. Dorsal flexion 

 is very limited. 



Dorsal flexion appears to l)e checked mainly by the deep flexor tendon, since in cases of rup- 

 ture of the hitter the toe turns up. Tlie sUght mobihty of the posterior part of the socket for the 

 second phahinx (formed by the third sesamoid) diminishes concussion when the weight comes 

 on the foot. 



LIGAMENTS OF THE LATERAL CARTILAGES 



In addition to the bands mentioned al)ove, which attach the lateral cartilages 

 to the extremities of the navicular bone, there are three ligaments on either side 

 which attach the cartilages to the phalanges. 



An ill-defined elastic band passes from the middle part of the border of the 

 first phalanx to the upper part of the cartilage, detaching a branch to the plantar 

 cushion. 



A short strong l)and connects the anterior extremity of the cartilage with the 

 rough eminence on the second phalanx in front of the attachment of the lateral liga- 

 ment of the coffin joint. 



The lower l)order of the cartilage is covered externally by fibers which attach 

 it to the wing of the third phalanx. 



The Articulations of the Pelvic Limb 

 the sacro-iliac articulation 



This joint (Articulatio sacro-iliaca) is a diarthrosis formed between the auricu- 

 lar surfaces of the sacrum and ilium. These surfaces are not smooth in the adult, 

 l)ut are marked by eminences and depressions, and are covered by a thin layer of 

 cartilage. The joint cavity is a mere cleft, and is often crossed by fibrous bands. 



The capsule is very close fitting, and is attached around the margins of the 

 articular surfaces. It is reinforced by the ventral sacro-iliac ligament (Ligamentum 

 sacro-iliacum ventrale), which surrounds the joint, and is exceedingly strong above. 



The movements ar(^ inappreciable in the adult — stability, not mobilitv^, 

 being the chief desi(U>i'atum. 



The following ligaments may be regarded as accessory to the joint, although 

 not directly connected with it. 



The dorsal sacro-iliac ligament (Ligamentum sacro-iliacum dorsale breve) is a 

 strong l)and which is attached to the internal angle (Tuber sacrale) of the ilium and 

 the summits of the sacral spines. 



The lateral sacro-iliac ligament (Ligamentum sacro-iliacum dorsale longum) 

 is a triangular, thick sheet which is attached in front to the internal angle and 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 ligament, below with the 

 sacro-sciatic ligament, and behind with the coccygeal fascia. 



The sacro-sciatic ligament (Ligamentum sacrospinosum et tuberosum) is a 



