Structural changes induced by cordotomy in the Nissl substance of identifiable spinal motoneurons innervating the white musculature of the European eel were quantified with the use of texture features calculated from digitized images. Data were evaluated and the motoneurons classified by using multivariate analysis. The study shows that there are differences in the structural organization of the Nissl substance of motoneurons taken from control and cordotomized fishes. Distinction could only be made by using texture features, as visual examination of the motoneurons did not reveal any alteration of the studied cellular substance. Reorganization of the Nissl substance might be the result of a changed protein metabolism or a changed neuronal activity pattern consequent upon cordotomy. The method employs quick and simple techniques and could be useful in several other neurobiological studies.