POSTERIOR TIBIAL GROUP. 251 



Rf-l'-i.tion. Posteriorly with the gastrocnemius and flexor 

 perforatus ; anteriorly with the tibia ; internally with the flexor 

 pedis accessorius ; externally with the peroneus. 



Action. To flex the phalanges, and assist in extending the 

 tarsal joint. 



FLEXOR PEDIS ACCESSORIUS. 



(Flexor Obliquus Peroneo-phalangeus. ) 



(Fie. 86. rf.) 



This muscle is situated on the posterior part of the leg, be- 

 tween the popliteus and flexor pedis perforans. It is fleshy, with 

 numerous fibrous intersections, and inferiorly a terminal tendon. 



Origin. From the external tuberosity of the tibia, and some- 

 times slightly from the fibula ; the tendon commences just above 

 the tarsal joint, and passes through a theca on its internal aspect. 



Insertion. It joins the tendon of the flexor perforans at 

 about a third from its commencement. 



Relation. Posteriorly with the gastrocnemius and flexor 

 perforatus ; anteriorly with the perforans, the popliteus, and the 

 posterior tibial artery. 



Action. To assist the flexor pedis perforans. 



POPLITEUS. 



(Femoro-tibialis Obliquus.) 

 (Fie. 86. a.) 



Situated at the back of the tibia, just below the stifle joint, 

 this muscle is triangular and fleshy, the fibres passing obliquely 

 downwards and inwards. 



Origin. By a tendon from a fossa outside the external con- 

 dyle of the femur ; it is attached to the capsular ligament of the 

 stifle joint. 



Insertion. The triangular surface on the supero-posterior part 

 of the tibia, and the upper portion of its internal border. 



Relation. Posteriorly with the gastrocuemius and flexor 

 perforatus ; anteriorly with the tibia, the capsular ligament, and 

 the tibial vessels ; externally with the flexor pedis perforans and 

 accessorius ; internally with the biceps rotator, and tibial fascia. 



Action. It flexes the leg, rotates it inwards, and tenses the 

 capsular ligament of the stifle joint. 



