Some morphological features of neurons in the rat spinal ganglion.

By means of serial sections in different planes, the perikarya in the rat spinal ganglion were found to be of an irregular spherical shape, with the largest maximal diameter and perimeter in tangential sections. Type-I and type-II neurons have a mean size of about 18 micrometers and 13 micrometers, respectively. Since some type-I perikarya are in the range of type-II cells, it is not possible to distinguish them from type-II cells in unstained thick sections. Some type-I cell perikarya exhibit areas with a reduced number of organelles. These cells are considered as being in a generating state, a fact finally leading to an age-dependent loss of neurons.