G.F.
From your description this sounds as if you have freezing damamge to the
tissues.
It may be that the size of your tissue is such that even though you are
carrying out rapid freezing the inner parts of the tissue are not getting
frozen at a rapid enough rate and ice crystals are forming. 
I am not sure of the size of a Finch brain, however I assume that it must
exceed that of national and local politicians.
Barry

>Return-Path: 
>Date: Thu, 29 Nov 2001 02:22:30 -0500 (EST)
>From: Gnf24@aol.com
>Subject: HELP???
>To: histonet@pathology.swmed.edu
>
>Helloo Histo techs....
>I am having a very difficult time getting good tissues of  Finch brains. I 
>fix tissue in 4% paraformaldehyde. Afterwards in series of sucrose b4
gelatin 
>embedding then fast freeze.  After cutting, (-12 c in cryostat)I see "swiss 
>cheese" type of tissue. It's wht our lab call tissue lysing. I can't figure 
>out wht's going on....... can anyone help me? pls?
>thanks
>G.F.
>
>
>