14 OHIO STATE ACADEMY OF SCIENCE. 



PRESIDENT'S ADDRESS. 



THE DOCTRINE OF NERVE COMPONENTS AND SOME 

 OF ITS APPLICATIONS. 



By C. Judson Herrick. 



The original purpose of the students of nerve components 

 was the analysis of the peripheral nervous system into units which 

 should have at the same time a functional and a structural signifi- 

 cance. This obviously is not the case with the cranial and spinal 

 nerves as commonly enumerated. The structural peculiarities 

 of each of the twelve pairs of cranial rierves, for instance, while 

 fairly well defined in the human body, are very diverse in the 

 vertebrate series as a whole. Thus the facial nerve from being 

 predominantly sensory in lower vertebrates (more than half of its 

 fibers in fishes belonging to a sensory system not represented at 

 all in mammals) becomes in man predominantly motor with only 

 a vestigeal remnant of the sensory components, and even the 

 motor component innervates chiefly muscles new to the mammalia. 

 We might multiply illustrations of the structural instability of the 

 cranial nerves. And that the cranial nerves have any special sig- 

 nificance as functional units cannot be maintained for a moment, 

 no two pairs in the human body having even approximately the 

 same function. 



But the first measurably complete analysis of the cranial 

 nerves into their components for their entire extent showed at 

 once the presence of certain structural and functional systems of 

 components, the laws of whose distribution have apparently little 

 to do with the serial order of the cranial nerves as commonly 

 enumerated. 



We have, then, a number of systems of components each 

 of which is defined structurally by similarity of peripheral and 

 central terminal relations, and functionally by the transmission of 

 nervous impulses of the same type or modality. Among these 

 systems are tactile, auditory, visual, olfactory, motor, gustatory, 

 etc., each with very characteristic terminal relations. 



Now, this structure is absolutely meaningless apart from 

 its function. Let any one who doubts this spend a few months 

 (as I have done) in trying to master and correlate the existing 

 literature of the cranial nerves of vertebrates. Though these 

 descriptions were for the most part written by famous masters of 



