I have twice published photographs of sections cut from blocks that were
over 30 years old.  Figures 1, 2, and 6 of "A study of hair groupings in
Primates" (Adv. Biol. Skin 9: 357-367) are of sections from blocks dating
from early in my mentor's career.  Two figures in "Zirconyl hematoxylin: a
new stain for acidic mucins" (Biotech. Histochem., in press) are from blocks
that I embedded 31 years ago.  I don't recall whether my mentor had sealed
his old blocks or not.  I did not deliberately seal my old blocks, but a
summer A/C failure sealed them for me about 2 years after the first sections
were made.  In neither case are the sections from old blocks worse than
sections from new blocks.
			Allen A. Smith
			School of Graduate Medical Sciences
			Barry University
			Miami Shores, FL  33161-6695