Evidence for three populations by size in L5 spinal ganglion in man.

In recent morphometric studies of the cytons of lumbar motoneuron columns, it was possible to discriminate various populations by the criterion of size. It was felt that the use of celloidin embedding, optimal enlargement to increase the number of counting windows, and the use of improved morphometric analysis had been important to this discrimination. Employing the improved methods of histologic preparation and morphometry to a study of the L5 spinal ganglia of man, it has been possible to show tentatively that there are at least three populations of cytons by diameter. The average number of large, intermediate and small cytons were 11,429, 31,675, and 25,389 respectively. It should now be possible to test whether selective congenital absence or degeneration of any of these three populations of cell bodies is found in disorders affecting primary afferent neurons.