FIXATION
Fixation of the pancreas should be as soon after death of the fish as possible, as autolytic changes can rapidly occur in the tissue, which makes any pathological alterations difficult to interpret. It is normal in paraffin sections to fix the pancreas attached to the intestine, as it is friable and can get lost in a fixative container. In salmonids it is advisable to cut off the tips of the pyloric caecae to assist rapid fixation. 100% neutral buffered formalin or Bouin's fluid are normally used in most laboratories for fixing the pancreas. For the demonstration of the secretory cells of the islets of Langerhans, it is recommended to use Bouin's Fluid, but to omit the acetic acid.

STAINING METHODS
For the exocrine tissue, the haematoxylin and eosin (H&E) method is adequate for routine staining. Obviously, when microorganisms are suspected, either Gram's or modified Gram's method should be used. For acid-alcohol-fast organisms (Mycobacterium), the Ziehl-Neelson method is recommended. The periodic-acid Schiff (PAS) and trichome stains are useful accessories to respectively demonstrate mucopolysaccharide and connective tissue. To demonstrate the secretory cells in the islets of Langherans, a modified aldehyde fuchsin/phloxine stain. (Bucke, 1972 & 1989).