Visualization of the HRP reaction product using the polarization microscope.

The reaction product of horseradish peroxidase (HRP) staining can be visualized with considerable contrast using the polarization microscope. This is illustrated on whole mount preparations of the cat retina which were stained after injection of HRP into the superior colliculus. When the specimen is placed between two crossed polarizing filters, the stained cells appear rather bright, in contrast to the other components of the tissue which remain dark. The visualization with the polarization microscope was compared with bright-field and dark-field illumination and was found to be superior to them.