ANATOMY OF THE HORSE. 83 
Development. —The extremities, originally epiphyses, become 
apophoses prior to the adult period. 
FIBULA. 
This small and seemingly unimportant bone can be regarded 
but as an appendix to the tibia. It is a long, slender, pyramidal 
Done, affixed to the external side of the tibia by a cartilago-liga- 
nentous substance, similar to that which binds the splint bones 
:o the cannon. 
Its superior part or head is bulky, flattened from side to 
>ide, and roughened—externally, by the attachment of the pe- 
oneus and the lateral ligament ; internally, by its cartilago-liga- 
nentous connexion. 
The inferior part, slender and tapering, extends about half 
■vay down the tibia, whence a ligament is continued 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 
s therefore analogically regarded as the carpus; so, in like man¬ 
ner, the hock becomes the correspondent part to the instep, and 
s consequently considered under the technical appellation of tar¬ 
ns. Six small bones enter into its composition: they are—the 
istragalus, os calcis, os cuboides, and the ossa cuneiforma, ex- 
emum, medium, and internum. 
THE KNUCKLE BONE. (ASTRAGALUS.) 
Situation— Uppermost bone of the hock: the bone which alone 
supports the tibia. 
Form —Distinguished by its pulley-like formation. 
Division —Into superior, inferior, and posterior surfaces. The 
superior or pul ley-like surface is entirely articulatory, and con¬ 
sists of two bold semi-circular prominences, with a deep capacious 
groove between them: the whole admirably adapted to the two 
grooves parted by their middle projection in the lower extremity 
-)f the tibia.— The posterior surface , extremely irregular, exhibits 
our polished places for articulation with the os calcis; and, be- 
ween them, asperous porous interspaces for ligamentous attach¬ 
ment.— The injerior surface , smaller than either of the others, is 
rregularly flattened, and almost wholly articulatory : it is em- 
iraced by the superior part of the large cuneiform bone. From a 
)it at the foot of the pulley-like adaptation, takes its origin the 
'xtensor pedis accessorius. 
