In the first third of the twentieth century, neuropathology seemed to offer the key to unlock the causes of psychiatric illness. Among the top centers devoted to the microscopic anatomy of the brain was that of Károly Schaffer in Budapest. Schaffer, a pioneer in the histopathology of Tay–Sachs–Schaffer disease, was also a charismatic teacher, bringing forth a school of investigators in psychopathology. Among them was László Meduna, who originated convulsive therapy. Despite the importance of the Schaffer school, it is almost unknown outside of Hungary, largely the result of the introduction of neurophysiological, neurochemical and molecular genetic methods that distracted attention away from histopathological contributions in psychiatry after the Second World War. The microscopic study of the brain and its diseases seemed increasingly less important.

The present biographical account of Károly Schaffer and his school seeks to bring this important story in the early history of biological psychiatry to a wider audience and explain why it has since been forgotten.

We hyposthesized that henna staining could provide an alternative to eosin when used as a counterstain to hematoxylin for understanding basic neurohistological principles. Therefore, this study was aimed at investigating the suitability of henna as counterstain to hematoxylin for the demonstration of the layer stratification and cellular distribution in the brain tissue. Henna stained nervous tissue by reacting with the basic elements in proteins via its amino groups. It stained the neuropil and connective tissue membranes brown and effectively outlined the perikarya of neurons with no visible nuclei demonstrating that it is an acidic dye. Henna as a counterstain to hematoxylin demonstrated reliability as a new neurohistological stain. It facilitated identification of cortical layer stratification and cellular distribution in brain tissue sections from Wistar rats. This was comparable to standard hematoxylin and eosin staining as morphological and morphometrical analyses of stained cells did not show significant differences in size or number. This study presents a method for staining with henna and demonstrates that although henna and eosin belong to different dye groups (anthraquinone and xanthenes, respectively) based on their chromophores, they share similar staining techniques and thus could be used interchangeably in neurohistology.