Abstract
A simple, rapid technique has been developed for the visualization of histamine in its cellular depots throughout the body. Based on the yellow fluorochrome formed by the interaction of o-phthalaldehyde and histamine, this procedure permits direct fluorescence microscopy of the "histaminocytes." Study of fresh blood and tissues from man and many animals revealed histamine its the mast cells, blood vessels, gastric mucosa, and in some species, platelets.