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Charles R. Bardeen 
does not at this period completely overlap the sciatic nerve and the two 
cutaneous nerves have a free path for growth. In Embryo XXII, length 
20 mm. (Plate V, Figs. 1 and 2) but one cutaneous nerve can: here be 
distinguished. This is clearly the posterior cutaneous nerve. In subse- 
quent development the nerve is shifted from the posterior margin over a 
region corresponding to the original medial surface of the hmb-bud and 
gives rise to extensive branches. In Embryo XXII perineal and cluneal 
rami may be traced for a short distance from the main trunk. 
2. N. Suralis. 
The main trunk of the sural nerve (external saphenous) may be seen 
arising, through the N. cut. sural medialis, from the tibial nerve in Em- 
bryo CXLIV (Plate IV, Figs. 1 and 2). In Embryo XXII, Plate V, 
Figs. 1 and 2, it is well developed and branches may be traced over the 
dorsum of the foot. The main trunk of this nerve at this period occu- 
pies a much more lateral position than subsequently. With the develop- 
ment and shifting of the gastrocnemius muscle the trunk of the nerve 
near its origin becomes shifted toward the middle of the calf and buried 
between the two heads of the gastrocnemius muscle. 
3. N. Surae Lateralis. 
In Embryo CXLIV (Plate IV, Fig. 2) this may apparently be recog- 
nized as short branch. In Embryo XXII (Plate V, Fig. 2) it is not 
much more highly developed. Subsequently it too becomes shifted over 
the back of the calf, but its branches are supphed to the original posterior 
margin of the limb (the external surface of the leg) as well as to the 
back of the leg. One of these branches finally anastomoses with the main 
trunk of the sural nerve. Variations on the adult indicate that the latter 
may at times arise from the N. sure lateralis. 
4, Nn. Peronei. 
The superficial and deep branches of the peroneal nerve-may readily be 
distinguished in Embryo CXLIV (Plate IV, Fig. 2) but the terminal 
cutaneous rami are not clearly developed. In Embryo XXII (Plate V, 
Fig. 2) these cutaneous rami may be followed over the dorsum of the 
limb-bud. They seem to have a simple direct growth toward the areas 
they are subsequently to supply. 
5. N. Tibialis. 
The terminal cutaneous branches of this nerve likewise cannot be dis- 
tinguished in Embryo CXLIV (Plate IV, Fig. 1) but are clearly to be 
made out in Embryo XXII (Plate V, Fig.1). Like those of the peroneal 
