[Motoneural organisation of the anterior horn with respect to the peripheral nerves in the rat (as studied by the method of retrograde transport of horseradish peroxidase)(author's transl)].

The motoneuronal organisation of the anterior horn with respect to the peripheral nerves, is still imprecise due to methodological problems. The chromatolytic and Golgi methods have furnished some fruitful but incomplete data. The retrograde transport of horseradish peroxidase permits to obtain both the topography of cells and their dendritic tree. With such a method we studied the cervical enlargment of the rat's spinal cord. Each nerve is in relation with a column of motoneurons whose both the metameric extension and the exact topography in the anterior horn have been defined. An histogram of the cell volumes has been performed for some nerves. These data permit to discuss the possible significance of the topographical separation of the cells related to the girdle with those in relation with the distal part of the upper limb. The histogram shows that the small cells, claimed to be gamma motoneurons, are much more numerous than generally supposed. The significance of the dendritic tree, which seemed oriented selectively in the cranio-caudal axis, is discussed.