94
ARTHUR HUGHES
RATlo!B%f
n tra VENTRAL HORN CELLS FIXATION 2-4 DAYS AFTER OPERATION
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AGE AT AMPUTATION
FIG. 4. Data from counts of lumbar ventral horn cells in embryos of Eleutherodactylus after leg amputation at different ages. Filled circles: ratio of ipsilateral to
contralateral ventral horn cells, showing change in response from Phase II to
Phase III at 8 days, after which number of cells temporarily increases on amputated
side. Open circles: number of contralateral ventral horn cells.
distal segments of the leg were innervated to a greater extent by younger
cells than are muscles of the thigh and that the innervation of these distal
segments is mainly from the caudal pole of the ventral horn. When the
corresponding amputations are performed at 10 days (Fig. 6) at a time
when an arrest of turnover still ensues, we see that the result once more
is similar after amputation at either level, but that in both the ipsilateral
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