Cell Loss with Aging

There have been several techniques developed to determine the number of cells in the central nervous system, but the ocular micrometric method is at the present time the most consistent and dependable.

Abstract

There have been several techniques developed to determine the number of cells in the central nervous system. Probably the simplest and the most common technique has been the ocular micrometric method. This was originally used by Hammerberg in 1895 and while other techniques may be mentioned, it is at the present time the most consistent and dependable. It involves examination of tissue with the aid of a micrometer disc inserted into the ocular of a compound microscope. Cells which fall within the squares of the disc may then be counted and total counts made as well as graphs showing relative populations within any portion of the section. This is most useful in determining cell numbers within a brain stem nuclear structure since it is possible in serial section counting to obtain an impression of the cell population at any specific point. By examination in several planes, one may obtain a 3-dimensional impression of the nucleus, and to compare specific sites within the nucleus in a number of brain specimens when the nucleus is of similar size. Direct optical examination of tissue by the investigator also makes possible a differentiation of neurons from glial cells and discriminates fairly easily when there is an overlapping of cells.