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TEXT-BOOK OF EMBRYOLOGY. 



distance proximal to the origin of the median and, passing along the ulnar side 

 of the forearm, unites with the median to form the superficial volar arch. From 

 the artery of the arm, which is called the brachial artery, a branch develops 

 about the middle and extends distally along the radial side of the forearm. A 

 little later another branch grows out from the brachial just proximally to the 

 origin of the ulnar and extends across to, and anastomoses with, the first branch. 

 Then the portion of the first branch between its point of origin and the anasto- 

 mosis atrophies, leaving only a small vessel which goes to the biceps muscle. 

 The second branch and the remaining part of the first branch together form the 

 radial artery (Fig. 227) (McMurrich). 



Femoral artery ,- 



Sciatic artery . 



Popliteal artery <.- 



Peroneal artery ^ c 



Saphenous artery -- 



Dors, artery of foot -- 



n 



.sciatic artery 



' Femoral artery 



Popliteal artery 



Ant. tibial artery 



Peroneal artery 

 Post, tibial artery 



FIG. 228. Diagrams showing three stages in the development of the arteries 

 of the lower extremity. McMurrich. 



In the lower extremity the primary artery is a continuation of the common iliac 

 which, in turn, is a branch of the aorta. This primary vessel, the sciatic artery, 

 passes distally as far as the ankle. Below the knee it gives off a short branch 

 which corresponds to the proximal part of the anterior tibial artery. Just above 

 the ankle it gives off another branch which corresponds to the distal part of the 

 anterior tibial. As will be seen, these two parts join at a later period to form a 

 continuous vessel. At this early stage the external iliac artery is but a small 

 branch of the common iliac; but it gradually increases in size, extends farther 

 distally in the thigh as the femoral artery and unites with the sciatic near the 

 knee. Just proximal to its union with the sciatic it gives off a branch which 

 extends distally along the inner side of the leg to the plantar surface of the foot, 

 where it gives off the digital branches. This vessel is the saphenous artery in 

 the embryo, and disappears in part during further development. From this 



