THE HOCK 



389 



The external border is prominent and rough, and has a groove in its centre. 

 Depending from each side is a process (the internal and external malleolus 

 of human anatomy), serving to strengthen the articulation with the 

 astragalus, and the internal being considerably the longer. Between these 

 are two deep grooves, smoothly covered with cartilage, and having a projection 

 in the middle similarly clothed. The direction of these grooves is obliquely 

 forwards and outwards. Both the malleoli are lined with cartilage, which 

 enters into the joint. 



The Fibula is a slender bone, having a slight enlargement at its superior 

 extremity to form the head. On its inner surface thei'e is a layer of 

 articular cartilage to form the joint with 

 the tibia. Below it has a bulbous end, 

 which is free, and affords attachment to 

 the ligamentous fibres which connect it 

 with the tibia. Between the two bones 

 there is a considerable space, occupied by 

 a thin membrane. 



The Tarsus, or hock, is made up of 

 several bones connecting the tibia above 

 with the metatarsus below. It corre- 

 sponds with the ankle of man ; and if the 

 term wrist were to be applied to the 

 knee of the horse, as suggested by certain 

 writers, in order to be consistent the 

 hock must be called the ankle, which 

 would lead to endless confusion. The 

 better plan is to retain the names by 

 which these parts are known in our ordin- 

 ary language, and to adopt the nomencla- 

 ture of the anatomical school for any 

 scientific description. Thus the cai'pus 

 and tarsus of the anatomist are rendered 

 into the knee and hock of the horseman 

 without impropriety, and at the same time 

 without any chance of a misunderstanding. 



The tarsus consists of six bones, dis- 

 posed in two rows, the astragalus and os 

 calcis forming the vipper one, but the 

 former bone alone entering into the tibio 

 tarsal, or hock joint, with the tibia. 



The Astragalus {aa-rpdyaXos, a die) is 

 an irregular bone, situated in front of the 

 OS calcis, between the tibia and the os 

 scaphoides : it is divided into five sur- 

 faces : first, the supero-anterior surface, pulley-like and articulatory, cor- 

 responds with the inferior extremity of the tibia, and consists of two 

 semicircular prominences, separated by a deep groove, taking a course 

 obliquely outwards and forwards ; secondly, the inferior presents a smooth 

 convex surface with a roughened depi'ession posteriorly, for ligamentous 

 attachment, and articulates with the superior face of the os scaphoides; 



Fia. 36. — Internal View OF Tarsal Bones. 



2. Inferior extremity of the tibia. 



a. Internal malleolus. 



b. External malleolus. 



3. Os calcis. 



4 and 5. Surfaces of articulation on the 

 astragalus, which, together with 

 corresponding ones on the tibia, 

 form the great hinge-joint of the 

 skeleton. 



c. Tubercle on the astragalus for the attach- 



ment of ligaments 



6. Os scaphoides. 



7. — cuneiforme magnum 

 S. — cuneiform parvum. 



9. — Large metatarsal bone. 

 10. Internal f^mall metatarsal bone. 



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