Hedley,
            positive things to remember about celloidin are that

1. shrinkage and distortion is minimal compared to paraffin (approximately
5%)

2.    for most celloidin techniques no heat was involved and therfore
tissues could be left infiltrating for extended periods of time (and this
was usually a requirement)

3. thick sections in the order of  100 microns or greater could be cut and
provided valuable insight into the spatial organization of various tissues.
With confocal and other types of microscopy it is possible to optically
section these.

4.    very large blocks of tissue could be processed

I think that the abandonment of celloidin in favor of paraffin wax was
inevitable due to the time required for processing of  blocks and the skill
in producing and staining sections. However, I have not seen paraffin
sections of eye that can equal celloidin sections as regards the lack of
distortion and the clarity of staining and detail.
Barry.

Hedley David Glencross wrote:

> Hi everyone
>
> An interesting discussion re this subject. It shows the inventiveness of
> histology. The tedium of staining though, is only matched by the tedium
> of processing and cutting. Oh, and the joy of block storage.
>
> I should add that I'm not that old (yet!), using this method into the
> mid 1980's for processing whole eyes. I understand that it was finally
> abandoned in the early 1990's in favour of wax.
>
> Regards
> --
> Hedley David Glencross