ARTERIES OF HUMAN LOWER EXTREMITY 79 
inferius has practically disappeared. ‘The portion immediately 
beyond the distal end of the latter vessel lies upon the posterior 
surface of the interosseus membrane and gives origin to two 
branches. The remainder of the vessel is involved in the meshes 
of the rete calcaneum. 
The portion of the a. peronaea posterior superficialis which 
extends from the present termination of the a. poplitea super- 
ficialis to the proximal end of the r. communicans inferius per- 
sists to become a part of the adult a. peronaea. A large part of 
the remainder of the artery has. been lost, but the distal portion 
of the vessel can still be recognized as forming a projection upon 
the proximal aspect of the rete caleaneum. This portion of the 
artery can be traced through the meshes of the rete as far as 
the a. plantaris lateralis. 
The rete calcaneum is very extensive at this stage of develop- 
ment and occupies the concavity upon the medial side of the 
caleaneum and surrounds the deep flexor tendons in the 
malleolar region of the leg. 
The component parts of the a. peronaea are now recognizable. 
The proximal part is derived from the a. peronaea posterior super- 
ficialis. The part between the aa. flexor hallucis longus and 
tibialis posterior represents the entire r. communicans inferius. 
The immediately succeeding part, which rests upon the mem- 
brana interossea, is derived from the a. interossea. The terminal 
part of the artery consists mainly of the r. calcaneus lateralis of 
the a. peronaea posterior superficialis. The connection between 
the a. interossea and the part of the latter artery which gives 
origin to the caleanean branch is SugerE through the agency of 
the plexus caleaneum. 
The part of the a. interossea which takes part in the formation 
of the a. peronaea has been noted as giving rise to a branch, the 
r. coronarius, at the stage of 18 mm. At the present stage 
another branch arises from it, namely, the r. perforans. Both 
of them become branches of the adult artery. At the stage of 
22 mm. the r. coronarius can be traced around the posterior 
and medial aspects of the tibia almost as far as the a. tibialis 
anterior. The views expressed by Hyrtl upon the conversion 
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THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, No. 1 
