92 H. D. SENIOR 
Branches. The a. genu media is present at the stage of 18 
mm. The other branches appear at a later stage of the 
development. 
A. poplitea profunda. The course of this vessel is described 
on page 73. The part of the a. poplitea profunda which extends 
from the hiatus tendineus to the origin of the a. genu inferior 
medialis becomes the proximal part of the adult a. poplitea. 
The remainder of the artery is represented in part by the root 
of the a. genu inferior medialis. It is represented also by the a. 
recurrens tibialis posterior and by the second part of the a. 
tibialis anterior (p. 84). 
A. poplitea superficialis. The formation of this artery results 
from the gradual union which takes place between the proximal 
part of the embryonic a. tibialis posterior superficialis and that 
of the a. peronaea posterior superficialis. The vessel lies upon 
the posterior surface of the m. popliteus and has nearly reached 
completion at the stage of 22 mm. The a. poplitea superficialis 
persists as the distal portion of the adult a.. poplitea (p. 84). 
A. tibialis anterior. This vessel may be divided into four 
parts which correspond to the four embryonic components of 
the adult artery. 
The first part extends from the origin of the vessel to the root 
of the a. recurrens tibialis posterior. It corresponds to the 
whole of the r. communicans medius (p. 84). 
The second part occupies the immediate neighborhood of the 
origin of the a. recurrens tibialis posterior. It represents, like 
that artery, a persisting portion of the embryonic a. poplitea 
profunda (p. 84). 
The third part extends from the a. re¢currens tibialis posterior 
to a point immediately beyond the root of the a. recurrens 
tibialis anterior. It is derived from the proximal portion of 
embryonic r. perforans cruris (p. 68). 
The fourth part of the artery extends from the termination of 
the third part to the proximal end of the a. dorsalis pedis. It 
represents the entire a. tibialis anterior, pars distalis, of the 
embryo (p. 72). 
