308 The Ohio Journal of Science [Vol. XX, No. 8, 



once understood. Second, until the nerve component work on 

 the analysis of the cerebral nerves was well under way, there 

 was no particular reason for suspecting separate gustatory or 

 special visceral ganglia, and certainly no reason for suspecting 

 a separate source. Third, there very early became established,, 

 on the basis of the work of Froriep and van Wijhe, the idea that 

 the neural crest ganglia grow ventrally and form a contact with 

 the vestigal sense organs in the position of the epibranchial 

 placodes. This tended toward the conception that the neural 

 crest ganglia grew into contact with the ectoderm, rather than 

 that the ectoderm proliferates cells mesially that form a contact 

 with the neural crest portion of the ganglion, and later became 

 detached and added to it. 



There are serious theoretical objections to this earlier view,, 

 in addition to the fact that it is not true. 1st, the neural crest 

 proper forms, so far as we know, only general visceral and 

 general somatic ganglia; 2nd, contact with sense organs in the 

 vertebrate is always formed by the nerve growing out from the 

 ganglion and not by the ganglion itself; 3rd, the epibranchial 

 placode, with which the neural crest ganglion is supposed to 

 form a contact, has absolutely no resemblance to a sense organ, 

 gustatory or any other type. In addition to these three con- 

 siderations, there is the well established fact that the epi- 

 branchial placodes do form typical ganglion cells, which are 

 added to the neural crest portions of ganglia VII, IX and X, 



While we are on this topic of the possible significance of the 

 epibranchial placode, I should like to call attention to the 

 conception that occurs in most of our standard text books on 

 neurology, viz., that the epibranchial placodes represent 

 phylogenetic sense organs, which may move out of the ectoderm 

 and become buried in mesenchyme to form ganglia. This con- 

 ception, in my opinion, is entirely erroneous, if we are to depend 

 on histological and embryological evidence at hand. The 

 conception has secured a hold on the minds of neurologists, 

 apparently because it helps to fill in a series in the origin of 

 ganglia, in which the olfactory cell, acting both as a receptor 

 and as a conductor, is the simplest form. The epibranchial 

 placode, if conceived phylogenetically as a sense organ, is 

 thought of as moving out of the ectoderm and thus forming a 

 ganglion. This connects the olfactory with other ganglia more 

 detached from the ectoderm. Now, exactly the same line of 



