5o8 A MANUAL OF ANATOMY 



terior tibial, (2) the superior internal tarsal branch of the dorsalis 

 pedis, and (3) branches of the internal plantar, thus forming the 

 internal malleolar anastomosis. 



The external malleolar artery arises from the outer side of the 

 anterior tibial at a slightly lower level than the internal malleolar. 

 Its course is outwards beneath the tendons of the extensor longus 

 digitorum and peroneus tertius, and it is distributed over the 

 external malleolus, where it anastomoses with (i) the anterior 

 peroneal, (2) the posterior peroneal, and (3) the external tarsal 

 branch of the dorsalis pedis, thus forming the external malleolar 

 anastomosis. 



The veins which accompany the branches of the anterior tibial 

 artery are, in each case, arranged as venae comites, and they termi- 

 nate as tributaries of the anterior tibial venae comites. 



Varieties — i . Origin. — The vessel may arise from the pophteal at the upper 

 border of the popUteus muscle. In these cases it may descend on the 

 posterior surface of that muscle (this being the more frequent position), or it 

 may pass deeply in front of it. 



2. Course. — The vessel in the lower fourth of the leg may be found upon 

 the fibula instead of the tibia, in which cases it makes a sudden bend at 

 the ankle-joint to become the dorsalis pedis artery. In very rare cases the 

 vessel may become superficial at the centre of the leg instead of in the lower 

 fourth. 



3. Size. — The vessel is occasionally very small, and, if the diminution in 

 size is very pronounced, it may fail to furnish the dorsalis pedis artery, in 

 which cases that vessel is supplied by the anterior peroneal. 



Anastomoses round the Knee- Joint. — ^The arteries which take 

 part in these anastomoses are as follows : (i) the two superior, and 

 the two inferior, external and internal articular branches of the 

 popliteal ; (2) the long descending branch of the external circum- 

 flex of the profunda femoris ; (3) the anastomotica magna of the 

 superficial femoral: ; (4) the fourth perforating of the profunda 

 femoris ; and (5) the posterior tibial recurrent (inconstant), and 

 the anterior tibial recurrent, both of which are branches of the 

 anterior tibial artery. For the special anastomoses of the foregoing 

 arteries see the descriptions of the individual vessels, and Fig. 251. 



The anastomoses are divided into superficial and deep, the former 

 being placed superficial to the patella, and the latter being in contact 

 with the lower end of the femur and the head of the tibia. 



Three transverse arches are to be noted anteriorly as follows : 

 one lies in the substance of the crureus, just above the patellar i, 

 surface of the femur, and is formed by branches of the superior [i 

 external articular of the popliteal, and the deep branch of the | 

 anastomotica magna of the superficial femoral. A second arch ji 

 lies in front of the head of the tibia, near the superior surface, jj 

 and is formed by branches of the inferior external articular, ij 

 and the superior internal articular. A third arch lies in front ^ff 

 of the tibia just above the tubercle, and is formed by branches % 

 of the anterior tibial recurrent, and the inferior internal articular ?; 

 artery. 



