THE LIMBS OF THE HORSE 139 



femoro-tibial joint is Hexed, just as the plantaris muscle effects 

 mechanically simultaneous extension of these joints. 



The origin of the peronauis tertius is common to that of the long 

 digital extensor, namely, from the depression between the patellar 

 surface and the lateral condyle of the femur. The common tendon of 

 origin lies in the notch lateral to the tuberosity of the tibia, being here 

 furnished with a diverticulum from the synovial lining of the femoro- 

 tibial joint. 



Opposite the extreme distal end of the tibia the tendon splits to 

 allow the passage of that of the anterior tibial muscle, and then divides 

 into three limbs that are attached as follows : The lateral limb is 

 inserted to the calcaneus and the fourth tarsal bone (cuboid), and 

 with it is associated one end of middle transverse ligament; the 

 middle limb is connected with the third metatarsal bone ; while the 

 medial limb is attached to the third tarsal bone (lateral cuneiform) 

 and the proximal end of the second and third metatarsal bones. 



M. tibialis anterior. — The anterior tibial muscle lies between the 

 long digital extensor and the peronseus tertius on the one hand, and 

 the tibia on the other. Its origin is from the proximal part of the 

 lateral surface of the tibia and the adjoining part of the fibula. In the 

 middle of the leg it is intimately connected with the peronseus tertius. 

 A strong tendon begins before the tarsus is reached, pierces the cleft 

 in the tendon of the peronseus tertius, and then divides into two limbs. 

 The lateral of these ends on the proximal end of the third metatarsal 

 bone along with the middle slip of the tendon of the peronaeus tertius. 

 The medial limb, commonly called the " cunean tendon " in books 

 dealing with surgery, takes an oblique course to reach the combined 

 first and second tarsal bones (medial cuneiform) and the base of the 

 second metatarsal bone. 



The synovial sheaths (vaginvE mucosae) of tendons. — The 

 present is a convenient time at which to review the various synovial 

 bursas and sheaths associated with the tendons in the region of the 

 tarsus. The sheaths and bursas in the more distal part of the limb are 

 similar to those belonging to the tendons of the thoracic limb (q.v.). 



An extensive bursa lies between the tendons of the gastrocnemius 

 and plantaris from the point (about the junction of the third and distal 

 fourths of the tibia) at which these tendons twist round each other to 

 the level of the middle of the tarsus. A very much smaller bursa lies 

 anterior to the point of insertion of the gastrocnemius tendon to the 

 tuber of the calcaneus. 



Where the combined tendon of the flexor hallucis longus and 

 tibialis posterior lies in the canal behind the tarsus it is surrounded 



