338 



FASCIA AND MUSCLES OF THE HORSE 



Blood-supply .- 

 Nerve-supply- 



- Anterior tibial artery. 

 -Peroneal nerve. 



B. Plantar Group 

 1. Gastrocnemius (Figs. 268, 292, 296).— This muscle extends from the distal 



third of the femur to the point of the hock. 



Shaft of femu; 



Medial licad of 

 gastrocnemius 



Fascial band 



Lateral head of 

 gastrocnemius 



Long digital 

 flexor 



Tibialis poste- 

 rior 



It arises by two heads. 



Origin. — (1) Lateral head, 

 from the lateral supracondy- 

 loid crest (margin of the supra- 

 condyloid fossa); (2) medial 

 head, from the medial supra- 

 condyloid crest. 



Insertion. — The posterior 

 part of the tuber calcis. 



Action. — To extend the 

 hock and to flex the stifle 

 joint; these two actions, how- 

 ever, cannot occur simulta-^ 

 neously. 



Structure. — The two bel- 

 lies are thick, fusiform, and 

 somewhat flattened. They 

 are covered by a strong apo- 

 neurosis and contain tendinous 

 intersections. They terminate 

 toward the middle of the leg 

 on a common tendon, which at 

 first lies posterior to that of the 

 superficial flexor, but, by a 

 twist in both, comes to lie in 

 front of the latter. The deep 

 fascia blends with the tendon 

 throughout its length, and the 

 soleus muscle is inserted into 

 its anterior edge. A small 

 bursa (Bursa tendinis m. gas- 

 trocnemii) lies in front of the 

 insertion on the tuber calcis, 

 and a large bursa (calcanea 

 subtendinea) is interposed be- 

 tween the two tendons from 

 the twist downward to the 

 middle of the hock. The super- 

 ficial digital flexor lies between 

 the two heads and is adherent 

 to the lateral one (Fig. 582). 

 The term tendo calcaneus or 

 tendo Achillis is a convenient 

 designation for the aggregated 

 tendons in the distal part of the 

 leg which are attached to the 

 tuber calcis. 

 Relations. — Anteriorly, the stifle joint, the superficial digital flexor, popliteus, 

 deep digital flexor, popliteal vessels, and tibial nerve; medially (above), the semi- 



Joint capsule^ 



Medial malle- 

 olus 



Tendon of 

 digital flexor 



-Soleus 



-Lateral exten- 

 sor 



Flexor hallucis 



Tendon of gas- 

 trocnemius 



Superficial 

 flexor tendoyi 



Tendon of deep flexor 



Fig. 296. — AIusCLES of Right Leg of Horse; Posterior View 



