In about 40 rats, the sciatic nerve was divided bilaterally and the animals were killed 1-40 days later. The excised nerves were usually fixed in a 4% sol. of basic Pb acetate for 24 hrs., and imbedded in paraffin. Some were stained by 1% toluidine blue, some by hematoxylin and eosin. The cytoplasm of the proliferating Schwann cells was distinctly metachromatic, especially on the 3d and 4th day after transection. The metachromasia paralleled in intensity the rate of cytoplasmic increase, was limited to the Schwann cell cytoplasm, and was never present in the remnants of degenerating myelin sheaths and axis cylinders.