Neurons of the substantia nigra in the European bison.

The studies were carried out on the mesencephalons of four European bisons with two different Golgi procedures and stained according to the Nissl and Klüver-Barrera methods. Four types of neurons were distinguished in the substantia nigra of the European bison. Type I are fusiform cells which are most numerous in pars compacta of SN. From each pole of the perikaryon originate 1-3 dendritic trunks. The axon arises from the base of dendritic trunk or directly from the lateral surface of the perikaryon. Type II are triangular cells which are most numerous in pars reticularis of SN. The neurons give off 3 primary dendrites. The axon arises mostly from the base of dendritic trunk. Type III are large multipolar neurons with 4-5 thick dendritic trunks. The axon emerges directly from the surface of the perikayon. Type IV are piriform and rounded cells. They have two thick primary dendrites, which leave the cell body at one pole of the neuron. The thin axon emerges from the cell body near the dendrites.