68 ANATOMY OF THE RABBIT 



of the carpus) to insert on the second metatarsal. Transect, 

 but do not mutilate the muscle under it. 



48. Tibialis posterior (t. posticus) m.: Proximal third of 

 medial side of tibia; to first two phalanges of second digit, 

 mainly. Extends foot and second digit. This is a flat, thin 

 muscle and lies closely along the medial side of the tibia. The 

 tendon of insertion begins about the middle of the tibia, passes 

 through a shallow groove in the medial maleolus of the tibia 

 and under the proximal end of the second metatarsal to its 

 insertion on the second digit. 



49. Extensor digitorum longus m.: Lateral condyle of tibia ; 

 to middle and distal phalanges of digits. Extends toes and 

 flexes foot. This muscle is fusiform. Its proximal attachment 

 is by a single round tendon ; its belly is flat and wide and rapidly 

 narrows to the tendons which pass through the transverse 

 crural ligament with the tendon of the anterior tibial m. (47) ; 

 then passes unaccompanied through the cruciate crural ligament 

 (on the dorsum of the tarsus) before diverging to insert into 

 the four digits. Thus, this muscle is remarkably similar to the 

 extensor digitorum communis m. (23) of the antibrachium. 



50. Peroneal mm. : Lateral side of proximal end of tibia and 

 fibula; to lateral side of foot, mainly. The four peroneal 

 muscles lie along the lateral side of the tibiofibula, mainly 

 between the extensor digitorum longus m. (49) and the flexor 

 digitorum longus m. (46), and their tendons pass through the 

 peroneal notch (Fig. 16, PN), which lies on the caudal side of 

 the lateral maleolus of the tibia. The proximal ends of all four 

 muscles are more or less fused with each other and with the 

 flexor digitorum longus m. (46). The long anterior peroneal m. 

 (50a) is the least involved since it is free except for a narrow slip 

 which passes from its proximal end over the peroneal nerve and 

 joins the fibers of the flexor digitorum longus m. (46). The 

 peroneal tendons are held within the grooves through which 

 they glide by broad tendonous structures each of which is called 

 a retinaculum peroneum. The one over the peroneal groove is 

 the superior retinaculum peroneum. 



