Cliff,
            "please open barrels of worms carefully".
The degree of shrinkage that is encountered with soft tissues is generally
quoted
as 25-30%. This varies considerably between different tissues and within
tissues.
It depends, as Frieda has pointed out, on the fixative used, duration of
fixation
and type and length of processing procedure as well as the composition of the
tissue and the phase of the moon.
Generally, hard tissues that have been decalcified tend to shrink to a lesser
degree than soft tissue as can be seen from separation of these in
sections. With
hard tissue, acids in general can  swell tissues but there is usually
considerable
greater swelling in the subsequent washing.
Baker's data provides a useful starting point for comparison of fixatives
but as
it mostly uses gelatin and albumen blocks, cannot take into account the
differential shrinkage with different tissue components.
Other  important points to consider are the degree of compression when
cutting the
section and the partial  recovery of some tissues such as collagen when the
section is mounted on a water bath. Measurement of shrinkage from tissue
sections
is difficult  as section thickness is then another factor. It may be best to
surface stain the block and measure tissues and  compare to cut surface of the
original unfixed block if posible.
For frozen sections,  soft tissue shrinkage is generally quoted as 2% and for
celloidin processing as 4-5%.
Barry


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