THE VASCULAR SYSTEM 241 



of Cryptobranchus suggests that the two superficial vessels may be 

 called V. lateralis cruris and V. medialis cruris on the tibial and 

 fibular sides respectively, and the deep vessel the V. interossea. 



The main factors of the V. lateralis cruris. 



(a) A plantar vein from the skin of the sole of the foot as well as 

 from the muscles of the same region. 



(b) A cutaneous factor from the plexus covering the extensor surface 

 of the leg. Through this plexus communication with the V. medialis 

 cruris is established. 



(c) A fairly large factor from the deeper muscles enters the V. 

 lat. cruris at about the middle of the leg. This factor anastomoses 

 with one from the V. interossea. 



(d) Just proximal to the knee one or two cutaneous factors from 

 the flexor side of the leg are received. 



(e) At about the same level a small muscular factor from the inser- 

 tion of the M. pub. isch. tib. and the tissues around the knee-capsule 

 enters the vessel. 



At the knee the vein turns somewhat dorsalwards and passes into 

 the thigh, dorsal to the M. pubo-tibialis, to join the F. circumflexa 

 genu, which is itself a factor of the V. ischiadica. 



On the post-axial or fibular side of the limb the V. medialis cruris 

 arises from the Arcus venosus dorsalis pedis and receives a large 

 factor from the dorsal plexus of the leg, whereby communication 

 with the V. lat. cruris is established. Just distal to the knee it may 

 receive a factor which drains the extensor and flexor muscles and lies 

 close to the external border of the fibula, or this factor may enter the 

 V. poplitea separately. At about the same point it receives a cutan- 

 eous factor which probably represents the V. cutanea lat. sup. 

 (Gaupp) of the Frog. The main vein then turns into the thigh 

 proximal to the knee and immediately dorsal to the MM. ischio- 

 flexorius and flexor fibularis, between which muscles and the M. 

 extensor ilio-tibialis it joins the V. poplitea. 



The F. interossea is the largest of the three crural veins, and, as 

 already mentioned, passes along the interosseal space together with 

 the corresponding artery and nerves. It arises from the middle part 

 of the Arc. ven. dors. ped. by factors which cross the dorsal side of 

 the tarsus, deep to the extensor muscles, and unite to form a single 

 trunk at its proximal edge. During the course of the vein down the 

 leg it receives several factors from the surrounding muscles. Within 

 the bend of the knee a cutaneous factor from the flexor side of the 

 leg is received, as well as the V. medialis cruris. The vein may now 



4038 R 



