THE POSTEBIOB LIMBS. 



143 



terminates in a blunt point, and gives attachment to the ligamentous fibres that 

 unite it to the tibia. 



The fibula is sometimes continued to the external inferior tuberosity of the 

 latter bone, with which it is confounded ; and as this tuberosity always forms a 

 special nucleus, particularly in the young Foal, it seems natural, having regard 

 to the disposition observed in Pachyderms and the Carnivora, to consider it as the 

 inferior extremity of the fibula fused to the tibia. In these animals, indeed, the 

 tuberosity or external maleolus is formed by the inferior extremity of the fibula. 



Structure and development. — This bone is very compact, and apparently 

 developed by a single nucleus of ossification ; though, in reality, there are two, 

 one of which is for the head of the bone. 



3. Patella (Figs. 95, 96). 



A small, short, and very compact bone, situated in front of the femoral 

 trochlea, and annexed to the tibia, to which it is attached by three extremely solid 

 ligamentous bands. 



The small polyhedron which it represents only offers for study three faces : 



PATELLA OF THE HORSE (SUPERIOR AND 

 POSTERIOR FACES). 



1, Superior face ; 2, posterior articular face ; 

 3, external border. 



PATELLA OF THE HORSE (ANTERIOR FACE). 



1, Anterior face ; 2, external border ; 3, 

 internal border. 



the superior, roughened, and serving for the insertion of the triceps cruralis and 

 rectus muscles ; the anterior, convex and irregular ; and the third, the posterior, 

 moulded on the femoral trochlea, to which it is but imperfectly adapted. In the 

 fresh state, however, the articular surface formed by the latter face is completed 

 by a fibro-cartilaginous apparatus, which will be noticed when describing the 

 femoro-tibial articulation. This articular surface is composed : 1. Of a median 

 ridge, which occupies the bottom of the trochlear cavity. 2. Of two depressed, 

 gliding, lateral facets on the sides of this cavity ; the internal facet is always 

 larger than the external — a disposition which permits the patella of one hmb to 

 be distinguished from that of the other. 



The Patella of the Ass is usually narrower than that of the Horse, but this 

 feature would scarcely permit of its being distinguished from that of the other 

 domestic Equidae. 



