THE BLASTEMA

A cone-shaped, 9-day regenerating limb blastema on the arm (brachium) of an axolotl (Ambystoma mexicanum) larva; amputation (plane approximated by the line) was through the neck of the humerus. Microscopically, this blastema consisted of a conical mass of mesenchymal cells (see next picture) capped by epithelium (arrow). Nerves, normally required for regeneration, do not stain in the procedure employed here (hematoxylin and eosin); cartilage and muscle, per se, were absent at this stage. Regeneration in the axolotl larva, under the conditions in which this specimen was maintained, normally reaches anatomical completeness within 30 days of amputation; magnification: 50 X.

<--- Blastemic mesenchyme.
The arrows point to mitotic figures; same specimen as in the previous picture but at 450 X.