2o8 STRONG. [Vol. X. 



3. Bearings upon the Classification and Segmentation 



of the Nerves. 



The foregoing comparative study of the cranial nerves shows 

 that the present mtmerical classification is unphilosophical. 



One principal cause lies in the fact that the classification, 

 with its serial numbering of the nerves, is based upon the con- 

 ditions existing among the higher vertebrates. Now, as we 

 have seen, the cranial nerves of the higher vertebrates have 

 undergone considerable reduction of primary components. 



Much time has been spent in ascertaining whether those 

 preauditory roots, issuing from the tuberculum acusticum and 

 lobus trigemini, belong to the V or VII nerves. For con- 

 venience and to emphasize their distinction from the V they 

 have been considered in this paper as belonging to the VII, in 

 accordance with recent researches. If, however, we take the 

 cranial nerves of the higher vertebrata as a basis, which is 

 practically done in the existing nomenclature, these components 

 or roots in question do not belong to either the Trigeminus or 

 Facialis ; they are actually different nerves from either of the 

 above, existing in the lower but not in the higher vertebrates. 

 The principal reason they have been assigned by recent investi- 

 gators to the VII is because their branches have been shown 

 to originate from these roots lying caudad of the Trigeminus 

 proper, and, consequently, by implication, belonging to the 

 segment of the VII. This, however, is not logical, inasmuch 

 as segmental character is not the basis of existing nomenclature, 

 nor, indeed, would it be possible with our present knowledge to 

 propose a nomenclature for the cranial nerves on this basis. 

 Furthermore, it has not actually been determined to what seg- 

 ment or segments these special cutaneous roots belong. 



It will therefore ultimately be necessary to remodel our cranial 

 nerve terminology, but, in my opinion, their exact composition 

 has not yet been sufficiently determined in order to do this 

 successfully. 



It may be well to indicate here the weak point in Gaskell's 

 analysis of the nerves (23 and 24), namely, that it does not 

 take account of all the qualitative differences among them. 



