THE VASCULAR SYSTEM 217 



The sciatic artery (A. ischiadica) now passes into the leg behind 

 the knee and there divides into two terminal branches, viz. the A. 

 plantaris (iv), a very short vessel which almost immediately divides 

 into lateral and medial rami, and the A. interossea (v) which, like 

 the nerve of the same name, passes to the extensor side of the leg. 



The R. plantaris lateralis (Manno) passes to the tibial side of the 

 leg, and sends a branch which becomes superficial at the lateral 

 border of the insertion of the pars plantaris of the M. ischio-flexorius, 

 and then gives off a R. descendens and a R. ascendens. The R. 

 descendens passes down the leg to the sole of the foot, while the R. 

 ascendens turns backwards to the lateral aspect of the knee and is 

 distributed to xhe pars plantaris of the M. ischio-flexorius and to the 

 insertion of the M. pub. isch. tib. The remainder of the R. plantaris 

 lateralis continues down the leg on the mesial side of the tibia to the 

 sole of the foot, and supplies the short flexor muscles of the tibial side. 

 During its passage through the leg it gives a twig to the M. pronator 

 profundus and to the M. interosseus. 



The R. plantaris medialis (Manno) passes out to the fibular side of 

 the leg, deep to the M. flexor primordialis communis, and immedi- 

 ately superficial to the M. caput longum musculorum contrahentium, 

 in company with the N. fibularis. As it turns distalwards down the 

 leg it gives a fairly large cutaneous branch to the flexor surface — A. 

 cutanea cruralis medialis (Gaupp). It also supplies the muscles named 

 above and then comes to lie — together with the accompanying nerve 

 — close against the surface of the fibula. At the tarsus a cutaneous 

 branch is given off to the skin on the fibular side of the ankle and a 

 deep muscular branch to the MM. flexores accessorii, medialis and 

 lateralis. It then continues along the fibular border of the tarsus to 

 the base of the fifth metatarsal, where it turns mesially to supply the 

 short flexor muscles of the fibular side of the foot. 



(v) A. interossea (Zuckerkandl). 



A. perforans cruris ....... (Manno). 



A. tibialis medialis ....... (Osawa). 



Immediately after reaching the extensor side of the M. interosseus 

 the interosseal artery gives off a superficial branch. 



(yd) A. interossea externa (O'Donoghue, in Sphenodon). 



R. dorsalis cruris ...... (Zuckerkandl). 



A. perforans superior ....... (Osawa). 



This artery supplies the skin on the dorsum of the leg — A. cutanea 

 cruralis lateralis — and the extensor muscles. It lies on the tibial side of 

 the A. interossea and is separated from it by the corresponding vein 



