You did not give your processing schedule??? And in what kind of instrument?? 

Dry, friable and often hard animal tissues after processing can be due to
several things. 

Animal tissues are leaner, have less fat and cannot withstand overexposure
aka 'overprocessing" to solvents during processing. This can be adjusted by
shortening processing time in alcohol gradient, xylene, and paraffin. 

Heat is a factor - eliminate heat during processing schedule, and minimize
time in paraffin, keeping temperature close or at paraffin melting point. 

Xylene tends to harden tissue, but is less sensitive to water carryover.
You can improve sectioning by using Clearite 3 (Richard Allan) or Propar in
place of xylene.  OR first change in xylene, then second change in Clearite
3.  

Soaking will work, but oversoaking can swell tissue out of block (feel the
surface of block face after cold soak).  Warm water, followed by cold water
or ice water (solid block of ice with water on top) helps, but make sure
you do not cut away that thinly soaked area of tissue or you have
sectioning problems again. 
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu