Abstract
1. The application of the rosindole reaction of E. Fischer to the histochemical localization of indole derivatives is described. This method demonstrates predominantly the tryptophan moiety of proteins and it therefore depends on the degree of protein fixation produced by formaldehyde.
2. The specificity of the rosindole reaction is established and the comparison is made between it and both the xanthydrol and post-coupled benzylidene reactions.
3. The facility of the histochemical technique as well as its specificity, sensitivity, and sharp localizability recommends the use of the rosindole reaction in routine histopathological investigation.