The Black Reaction - La reazione nera The Purkinje cell of the
cerebellum is used as an example to illustrate the revelatory
power of the Golgi stain, and why it was and still is important.
The extension and orientation of dendrites of the Purkinje cells
provided a key for the understanding of how the cerebellar
cortex is built up and works (the same could be stated for all
other structures of the brain, in which how neuronal processes
are arranged is the prerequisite for their functioning). The
anatomist Evangelista Purkinje described the large cells in the
cerebellum (A) that bear his name. With the methods available at
Purkinje's time, he could only observe the cell bodies. No
branches can be seen even in the routine histological stains
(thionin, cresyl violet) still used nowadays (B). C demonstrates
that the Golgi stain fully visualizes the entire extent of
ramifications of this particular neuronal cell type and its
spatial orientation. This is crucial for the functioning of the
cerebellar cortex, since t