The Cajal and Bielschowsky silver methods are later developments of the silver impregnation methods. They are used to demonstrate axons, neurofibrils, and nerve endings, including synapses. Originally used on blocks of tissues, they have been modified for use on mounted sections. Demonstration of the myelin sheath is accomplished by a variety of methods, including osmium tetroxide, Pal-Weigert, Weil, and Marchi techniques. The shape of neurons varies with the number and arrangement of their processes.
Bipolar neurons are spindle-shaped, with one process at each end.
Multipolar neurons have polygonal cell bodies and many processes. Nissl material extends into the proximal portions of dendrites but is absent from axons and axon hillocks. Nissl substance undergoes definite changes in response to axonal injury. The Golgi area of the neuron is the site where carbohydrates are linked to proteins in the synthesis of glycoproteins. Neurofilaments are made of structural proteins similar to those of the intermediate filaments of other types of cells.