In most of the riiotor nuclei the ganglion cells are not unifomily distributed throughout the whole nucleus. They are grouped into several iiiore or less distinct cluinps, some of which possess cells which differ in size and appearance from the others. These cell clumps a r e very generally believed to possess a definite relation t o the several branches of the nerve and tlie muscles they supply. Reviewing the literature dealiiig with this subject, we notice that the opinions of most authors concerning representation of the different muscles in tlie cell clusters of their nuclei are very contradictory. I n investigations on this subject the chroniatolytic nietliod was generally used. Even working on tlie same animal and with the same nietliods authors got different results, as can be seen in cake of the ocnlomotor nucleus, where the nuclear representation, a question of great practical value, was often investigated. C'oncerning other cranial motor nuclei the situation is very siniil a r.
Several years ago we (Szenthgothai, '41) introduced a new tecliiiique in order to deterniine the exact representation of iiinsclcs in their supplying nuclei which we believe to be much more suitable for this purpose than the clironiatolytic method. K i t h the aid of a stereotasic instrument, very similar to the well-known Horslep-Clarke apparatus, we mere able to prove '707