Deborah  - I spent many years preparing marine tissue using the processing
schedule below. We prepared fish tissue, bivalves, crustaceans, echinoderms,
polychaetes, and anything else (marine) of interest.  I rarely encountered
difficulty sectioning, and attributed this to the use of Methyl Benzoate.
It's not inexpensive, but it seems not to need changing as often as the
ethanols and xylene.  While I did my own grossing, thus assuring that
tissues were usually trimmed thinly enough, There were occasions where we
processed small, whole critters.  This processing schedule still rendered
the tissue adequately "cuttable" and preserved the morphology well.  We did
NOT do any immuno, so I have no idea if this schedule would work for those
procedures.  

An adequate volume of fixative is imperative.  Tissues remain in fixative
(usually Dietrich's, but NBF, Helly's and Davidson's were also used from
time to time) until 11:30 PM, then are processed as follows:

80% Ethanol for 1 hour
95% Ethanol for 1 hour
100% Ethanol for ½ hour
100% Ethanol for 1hour
Methyl Benzoate for 1 hour
Xylene for ½ hour
Xylene for 1 hour
Paraffin I for 1 hour (Temperature of paraffin MUST be only a few degrees
over the melting point)
Paraffin II for ½ hour
Paraffin III for 1 hour

My processor was set to make the first move (into 80% ethanol at 11:30 PM,
thus tissues were ready to be removed and embedded at 8:00 AM.

Joanne Lahey
Battelle
397 Washington Street
Duxbury, MA 02332-4546
E-mail:LAHEYJ@BATTELLE.ORG
Voice: (781)952-5341
FAX: (781) 934-2124

Date: 11 Mar 1999 07:00:45 -0600
From: Deborah Faichney <d.a.faichney@stir.ac.uk>
Subject: tissue processing

Hi ,

We work with fish tissues, mainly Salmonids.  Our pathologist has asked if
we can reduce the overnight processing to 16 hours from 21 hours, thus,
enabling him to announce urgent samples late afternoon!!

 We use a series of Industrial Methylated spirit, Ethanol, Chloroform then
Paraffin.  Our tissue samples can be quite large (up to 3cmx1cm), normally
they are below 5mmx5mm.

Any ideas or comments will be gratefully received.

Debbie Faichney
Institute of Aquaculture
Stirling University
Scotland