The measurement of motor cell volumes in rats

The volumes of cell bodies and nuclei of rat motoneurons were calculated from reconstruction in araldite embedded spinal cord. The results were compared with those obtained by applying formulae to two-dimensional measurements. The results show that the volumes of reconstructed cells have comparable values when derived from transverse and longitudinal sections. These values differ quite remarkably from those obtained by applying the formulae of the sphere and of a non-rotational ellipsoid. The difference is thought to reflect shape and orientation of the cells in the spinal cord. Nuclei were found to have a spheroidal shape, with the major diameter parallel to the axis of the spinal cord. There is also a linear relationship between cells and nuclear volume (with values varying between 5 and 15). The results of this study suggest that once reconstruction studies have shown the basic parameters of the cells, a graphical method for cell volumes from equatorial area measurements gives more satisfactory results than other proposed methods.