THE TIBIA 



103 



The distal extremity (Extremitas distalis) is much smaller than the proximal; 

 it is quadrangular in form and larger internally than externally. It presents an 

 articular surface (Cochlea tibia3), which is adapted to the trochlea of the til)ial 

 tarsal lx)ne (astragalus), and consists of two grooves separated by a ridge. The 

 ridge and grooves are directed obliquely forward and outward, and are bounded 

 laterally by the malleoli, to which the lateral ligaments of the hock joint are at- 



Spine 



Tuberosity 



Sulcus niusculnris -^ 

 External condyle - 



Head of fibula — 



Interosseous space -- 

 External surface 

 Shaft of fibula — 



External malleolus - 



- Groom far middle patellar ligament 

 r — Internal condyle 



Imprint for insertion of gracilis 



Crest 



— Imprint for insertion of semilendi- 

 nosus 



Internal surface 



-Internal walleolus 



Fig. 70 — Right Tibia and Fibula of Horse, Axterior View. 



tached. The internal malleolus (Malleolus tibialis) is the more prominent of the 

 two, and forms the anterior boundary of a groove for the tendon of the inner 

 head of the flexor perforans. The external malleolus (Malleolus fibularis) is 

 broader, and is marked by a vertical groove for the passage of the lateral extensor 

 tendon. 



Development. — The tibia has the usual three chief centers of ossification and 

 supplementary ones for the tuberosity and the external malleolus. The latter is 



