ARTERIES OF HUMAN LOWER EXTREMITY 89 
a. glutaea inferior, from the root of the a. pudenda interna, and 
from the part of the a. umbilicalis beyond the distal end of its 
dorsal root. The portion of the original a. umbilicalis which 
contributes to the formation of the a. hypogastrica is the source, 
in all probability, of all the visceral branches of the artery. The 
a. obtoratoria is not present at the stage of 22 mm. In conse- 
quence of the transference of the origins of the aa. iliolumbalis 
and sacralis lateralis to the a. glutaea superior, the proximal 
part of that artery becomes the posterior division of the a. 
hypogastrica. 
A. iliaca communis. This artery is derived from the portion 
of the dorsal root of the a. umbilicalis which lies upon. the 
proximal side of the origin of the a. iliaca externa. 
A. iliaca externa. This artery already springs from the con- 
vexity of the a. iliaca communis at the stage of 8.5 mm. Its 
termination is unbranched until a period shortly before the stage 
of 12 mm., when it divides into the a. epigastrica inferior and 
the a. femoralis. The a. circumflexa ileum profunda arise 
from the a. iliaca externa between the stages of 18 and 22 mm. 
A. interossea. The course of this part of the axial artery is 
described on page 73. 
The a. interossea is joined before the stage of 18 mm. by the 
distal end of the r. communicans inferius. The junction occurs 
at a point immediately beyond the inferior margin of the m. 
tibialis posterior. This artery has given origin to the r. coro- 
narius at the stage of 18 mm. and to the r. perforans and to 
the branch of communication with the a. peronaea posterior 
superficialis at the stage of 22 mm. 
The part of the a. interossea extending from the termination 
of the a. poplitea profunda to the distal end of the r. communicans 
inferius disappears between the stages of 18 and 22 mm. A 
vestige of the proximal end of this part of the artery sometimes 
persists in the form of a small branch of the a. tibialis anterior 
or of the r. fibularis. 
The small portion of the a. interossea which extends from the 
distal end of the r. communicans inferius to that of the membrana 
interossea persists as the third part of the a. peronaea (p. 79). 
