64 OSTEOLOGY OF THE HORSE. 



FIBULA. 



This small and seemingly unimjjortant bone can be regarded 

 but as an appendix to the tibia. It is a long, slender, pyramidal 

 bone, affixed to the external side of the tibia by a cartilago-liga- 

 mentous substance, similar to that which binds the splint bones 

 to the cannon. 



Its superior part or head \s bulky, flattened from side to 

 side, and roughened — externally, by the attachment of the pe- 

 roneus and the lateral ligament; internally, by its cartilago-liga- 

 mentous connexion. 



The inferior part, slender and tapering, extends about half 

 way down the tibia, whence a ligament is continued from its ter- 

 mination to the lower extremity of that bone. 



Connexion — With the tibia. 



OF THE HOCK. (tARSUS.) 



As the knee of the horse answers to the wrist of man, and 

 is therefore analogically regarded as the carpus ; so, in like man- 

 ner, the hock becomes the correspondent part to the instep, and 

 is consequently considered under the technical appellation of ta?-- 

 sus. Six small bones enter into its composition : they are — the 

 astragalus, os calcis, os cuboides, and the ossa cuneiforma : — ex- 

 ternum, medium, and internum. 



THE KNUCKLE BONE. (ASTRAGALUS.) 



Situation — Uppermost bone of the hock : the one which alone 

 supports the tibia. 



j.^0^^ — Distinguished by its pulley-like formation. 



Division — Into superior, inferior, and posterior surfaces. 



The superior or pulley-like surface is entirely articulatory, and 

 consists of two bold semicircular prominences, with a deep capa- 

 cious groove between them : the whole admirably adapted to the two 

 o-rooves, parted by their middle projection, in the lower extremity 

 of the tibia. — The posterior surface, extremely irregular, exhibits 

 four polished places for articulation with the os calcis ; and, be- 

 tween them, asperous porous interspaces for ligamentous attach- 

 njent. — The inferior surface, smaller than either of the others, is 

 irregularly flattened, and almost wholly articulatory : it is em- 

 braced by the superior part of the large cuneiform bone. From a 

 pit at the foot of the pulley-hke adaptation, takes its origin the 

 extensor pedis accessorius. 



OS CALCIS. 



Situation— liiovms the posterior projecting part, called the 

 point of the hock. 



