ASTRAGALUS. 93 



FIBULA. 

 (PL. L //.) 



This is a long slender bone, little developed in the horse, and 

 ia an appendage to the tibia, being attached to the outer side 

 of that bone, and extending from its head to its lower third, to 

 Tvbich it is affixed by a ligement ; the space between the two 

 bones is called the tibial arch. 



The head, or siiperio^ part, is nodular, somewhat flattened, 

 and roughened externally for the attachment of the external 

 lateral ligarnent of the joint above ; internally it articulates with 

 the external lateral part of the head of the tibia. I)istally the 

 bone becomes slender, and tapers to a point, from which a liga- 

 ment is sometimes continued the whole length of the tibia. The 

 peroneus muscle arises chiefly from the fibula. 



TARSUS. 



The tarsus, or hock, corresponding to the ankle-joint of a man, 

 is composed of six irregular, compact bones, placed between 

 the distal eiul of the tibia and the proximal end of the meta- 

 tarsus ; they are arranged in two series ; one. consisting of the 

 cuboid and three cuneiform bones, the magnum, medium, and 

 parvum, corresponds to the lov/er row of carpal bones ; the 

 other, or upper series, consists of the astragalus and calcaneum 

 the first, forming with the bone above the mobile portion of the 

 joint, may be said to correspond to the upper row of carpal 

 bones, while the latter, being the lever bone, corresponds to the 

 trapezium. These bones, like those of the carpus, are thickly 

 covered on their articular surfaces by cartilage, which acts as a 

 protection against concussion." 



ASTRAGALUS. 

 (Fia. 22. 2.) 



This, otherwise termed the os tali or ankle bone, is a pulley^ 

 like bone, placed immediately below the tibia, with which it 

 articulates. A very large proportion of the surface of this bone 

 is articular. 



The superior or supero-anterior surface presents an articular 



