FIBULAR REGION. 269 



flexor longus pollicis, flexor longus digitorum, posterior tibial vessels 

 and nerve, peroneal vessels, and in the sole of the foot with the ab- 

 ductor pollicis. By its deep surface with the interosseous membrane, 

 the fibula and tibia, the ankle joint, and the astragalus. The anterior 

 tibial artery passes between the two heads of the muscle. 



The student will observe that the two latter muscles change their 

 relative position to each other in their course. Thus, in the leg, the 

 position of the three muscles from within outwards, is, flexor longus 

 digitorum, tibialis posticus, flexor longus pollicis. At the inner mal- 

 leolus, the relation of the tendons is, tibialis posticus, flexor longus di-> 

 gitoram, both in the same sheath ; then a broad groove, which lodges 

 the posterior tibial artery, venae comites, and nerve ; and lastly, the 

 flexor longus pollicis. 



Actions. The popliteus is a flexor of the tibia upon the thigh, 

 carrying it at the same time inwards so as to invert the leg. The 

 flexor longus pollicis, and flexor longus digitorum are the long flexors 

 of the toes ; their tendons are connected in the foot by a short tendi- 

 nous band, hence they necessarily act together. The tibialis posticus 

 is an extensor of the tarsus upon the leg, and an antagonist to the 

 tibialis anticus. It combines with the tibialis anticus in adduction of 

 the foot. 



Fibular Region. 



Peroneus longus. 

 Peroneus brevis. 



Dissection. These muscles are exposed by continuing the dissec- 

 tion of the anterior tibial region outwards beyond the fibula, to the 

 border of the posterior tibial region. 



The PERONEUS LONGUS (u-s^ov*?, fibula, extensor tarsi fibularis lon- 

 gior) muscle arises from the head and upper third of the outer side of 

 the fibula, and terminates in a long tendon, which passes behind the 

 external malleolus, and obliquely across the sole of the foot, through 

 the groove in the cuboid bone, to be inserted into the base of the me- 

 tatarsal bone of the great toe. Its tendon is thickened where it glides 

 behind the external malleolus, and a sesamoid bone is developed in 

 that part which plays upon the cuboid bone. 



Relations. By its superficial surface with the fascia of the leg and 

 foot. By its deep surface with the fibula, peroneus brevis, os calcis, 

 and cuboid bone, and near the head of the fibula with the fibular 

 nerve. By its anterior border it is separated from the extensor longus 

 digitorum by the attachment of the fascia of the leg to the fibula ; and 

 by the posterior border by the same medium from the soleus and flexor 

 longus pollicis. The peroneus longus is furnished with three tendinous 

 sheaths and as many synovial membranes ; the first is situated behind 

 the external malleolus, and is common to this muscle and the peroneus 

 brevis, the second on the outer side of the os calcis, and the third on 

 the cuboid bone. 



The PERONEUS BREVIS (extensor tarsi fibularis brevior) lies be- 



