Regeneration from isolated half limbs in the upper arm of the axolotl.

A technique enabling the isolation of half limb stumps using strips of skin from the head is described. Using this technique posterior, dorsal and ventral halves of the upper arms of axolotls were constructed. All halves produced regenerates and regional differences were shown in the regenerative and regulative abilities of the different halves. Posterior half stumps regenerated limbs with a mean digit number of 3.9 and had a normal dorsoventral muscle pattern. Anterior halves produced hypomorphic limbs with a mean digit number of 1.2 while dorsal and ventral halves produced an average of 3.8 and 2.6 respectively. Regenerates from dorsal half stumps had a normal dorsoventral axis but the majority of those from ventral halves were either double ventral or had little muscle on the dorsal side of the limb.