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Charles R. Bardeen 29 
was found. In eight instances a branch passed from the n. plantaris 
medialis to the nerve to the 4th and 5th toes. In seven instances a 
branch passed from the n. plantaris lateralis to the nerve supplying the 
contiguous sides of the 3d and 4th toes. In two instances the n. plan- 
taris lateralis furnished the chief supply of the contiguous sides of the 
3d and 4th as well as of the 4th and 5th toes. In one instance the n. 
plantaris medialis supplied the contiguous sides of all the toes. 
VI. CUTANEOUS BRANCHES TO THE INFERIOR EXTREMITY FROM 
THE DORSAL DIVISIONS OF THE SPINAL NERVES. 
In Embryo CXLIV, length 14 mm. (Plate IV, Fig. 2), the lateral 
branches of the dorsal divisions of the last five or six thoracic and the 
first three lumbar nerves may be followed to the subcutaneous tissue. 
They take at this period a somewhat simple course and have a distinctly 
segmental arrangement. The dorsal divisions of the fourth and fifth 
lumbar and of the sacral and coccygeal nerves are connected by anasto- 
mosing branches. From these nerves rami may be followed toward, but 
cannot be followed distinctly into the skin. 
In Embryo XXII, length 20 mm. (Plate V, Fig. 1), the lateral 
branches of the first three lumbar nerves may be followed distally to 
the base of the limb where they terminate over the proximal margin of 
the iliac crest. The branches of the second and third lumbar nerves 
are connected at this period by anastomoses, although the plexiform 
arrangement characteristic of the adult is not yet apparent. In sub- 
sequent development these nerves extend over the postero-lateral surface 
of the thigh, nn. clunium superiores. For the variations in origin of 
these nerves in the adult, see Bardeen and Elting, ot. 
The lateral branches which arise from the dorsal divisions of the first 
three sacral nerves anastomose and from them in Embryo XXII two 
delicate branches may be traced toward the skin, nn. clunium mediales. 
There is considerable variation in these nerves in the adult, but I have 
not sufficient data on which to base a statistical study of the subject. 
VII. SUMMARY AND GENERAL CONCLUSIONS. 
The cutaneous nerves of the posterior limb in the embryo first ap- 
proach the anterior, posterior and distal margin of the limb-bud and 
from these areas send branches of distribution over the medial (ventral) 
and lateral (dorsal) surfaces of the developing limb. This method of 
development may be recognized in the adult. The chief nerve 
trunks approach the fascia in a line which corresponds fairly closely 
with the primary margins of the hmb. The posterior cutaneous 
