THE POSTERIOR TIBIO-FIBULAR REGIOX. 



525 



' Femur. ( 



external semilunar fibro-cartilage, and is invested by the synovia! membrane 

 of the knee-joint. 



Relations. By its superficial surface, with the fascia above mentioned, which 

 separates it from the Gastrocnemius, Plantaris, popliteal 

 vessels, and internal popliteal nerve; by its deep sur- 

 face, with the superior tibio-fibular articulation and 

 back of the tibia. 



The Flexor longus hallucis is situated on the fibular 

 side of the leg. It arises from the lower two- 

 thirds of the posterior surface of the shaft of the 

 fibula, with the exception of an inch at its lowest 

 part ; from the lower part of the interosseus mem- 

 brane ; from an intermuscular septum between it 

 and the Peronei, externally ; and from the fascia 

 covering the Tibialis posticus, which is attached to 

 the inner border of the fibula externally and to 

 the posterior surface of the tibia between the 

 origins of the Tibialis posticus and the Flexor 

 longus digitorum, internally. The fibres pass ob- 

 liquely downward and backward, and terminate 

 round a tendon which occupies nearly the whole 

 length of the posterior surface of the muscle. 

 This tendon passes through a groove on the pos- 

 terior surface of the lower end of the tibia; it 

 then passes through another groove on the pos- 

 terior surface of the astragalus, and along a third 

 groove, beneath the sustentaculum tali of the os 

 calcis, into the sole of the foot, where it runs 

 forward between the two heads of the Flexor brevis 

 hallucis, and is inserted into the base of the last 

 phalanx of the great toe. The grooves in the , 

 astragalus and os calcis, which contain the tendon ID 

 of the muscle, are converted by tendinous fibres 

 into distinct canals lined by synovial membrane ; 

 and as the tendon crosses the sole of the foot, 

 it is connected to the common flexor by a tendinous 



T J 



slip. 



Relations. By its superficial surface, with the 

 Soleus and tendo Achillis, from which it is sepa- 

 rated by the deep transverse fascia; by its deep sur- 

 face, with the fibula, Tibialis posticus, the peroneal 

 vessels, the lower part of the interosseous membrane, 

 and the ankle-joint; by its outer border, with the 

 Peronei : by its inner border, with the Tibialis 

 posticus and posterior tibial vessels and nerve. 



The Flexor longus digitorum (perforans) is situated 

 on the tibial side of the leg. At its origin it is thin 

 and pointed, but gradually increases in size as it 

 descends. It arises from the posterior surface of the 

 shaft of the tibia, immediately below the oblique line, to 

 within three inches of its extremity internal to the 

 tibial origin of the Tibialis posticus ; some fibres also 

 arise from the fascia covering the Tibialis posticus. The 



fibres terminate in a tendon which runs nearly the whole length of the posterior 

 surface of the muscle. This tendon passes behind the internal malleolus in a groove 

 common to it and the Tibiali.< posticus, but separated from the latter by a fibrous 

 septum, each tendon being contained in a special sheath lined by a separate synovial 



"14 



33-2. Muscles of the 



