Our work has been initiated by a number of misconceptions about the structure of the cranial nerve nuclei. Despite many recent findings in disagreement with the old concepts, these misconceptions survive in modern textbooks and cause many problems in comprehending the efferent outflow of the brainstem. We have approached these problems with a twofold stratagy. First, we have relied on the neural morphology in sorting out the different groups of nerve cells; second, we have done this on three distantly related animal species in order to compare the interspecies similarities and diversities. The double approach has its vulnerability. A voluntarist interpretation of the neural morphology may result in arbitrary groupings of neurons according to some preconceived view. We have been continuously aware of this possibility and have tried to be very careful about interspecies similarities or diversities. Second, using the data obtained only from three species for a comparative neuroanatomy study is like tiptoeing from tussock to tussock over a marshy field. Here we have also been aware of the danger of slipping into new misconceptions however carefully we proceed. The probable gaps should be filled and the misconceptions corrected in future works, but a few basic principles and some inferences may be offered from the present work as well.
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