82 H. D. SENIOR 
of the r. coronarius into the communicating branch and medial 
malleolar arteries of the adult have been noted above (footnote 
WO; th G3): 
A small portion of the a. peronaea posterior superficialis 
appears at the present stage as a branch of the a. peronaea. It 
runs upon the posterior surface of the m. flexor hallucis longus. 
The disintegrating a. interossea has left a similar vestige of its 
proximal end upon the posterior surface of its interosseous 
membrane. This vestigial branch occasionally persists as a 
branch of the adult a. tibialis anterior.11. The terminal part of 
the main trunk of the a. peronaea posterior superficialis is now 
involved in the rete caleaneum. It usually leaves its mark in 
the adult as a recurrent element among the leash of branches — 
known as the r. calcaneus medialis of the a. plantaris lateralis. 
The aa. iliolumbalis and sacralis lateralis now arise from the 
a. glutaea superior. The root of the latter artery has conse- 
quently become the posterior division of the adult a. hypo- 
gastrica. All the visceral arteries of the pelvis, with the excep- 
tion of the a. vesicalis superior, have assumed their adult 
relations. 
h. Changes occurring in the principal arieries subsequent to the 
stage of 22 mm. 
A. Formation of the adult a. poplitea and a. tibialis anterior. 
Fig. 10, AS Co The.) 22: B,C EXCrAl Cr Cr ls tne eae 
The r. communicans medius, the presence of which was noted 
at the stage of 22 mm., seems to arise at about that stage of 
development. In C. E. C., no 1, it is larger upon the right side 
than upon the left and in C. E. C, no. 6, which also measures 
22 mm., it is absent altogether. 
11 Mr. Kimbrig has kindly dissected six adult legs for evidence of persistence 
of this vessel. In two instances he found a branch accompanying the n. interos- 
seus cruris for a short distance. In both cases the branch arose from the root of 
the ramus fibularis. 
It is very questionable whether the B. N. A. is correct in classifying the r. 
fibularis as belonging to the a. tibialis posterior. It has usually been regarded, 
in English-speaking countries at all events, as a branch of the a. tibialis anterior. 
