DHE SDOCTRINE OF NERVE COMPONENTS AND 
SOME, OF ITS: APPLICATIONS:* 
By C. Jupson 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 struc- 
tural significance. This obviously is not the case with the 
cranial and spinal nervesas commonly enumerated. The struc- 
tural peculiarities of each of the twelve pairs of cranial nerves, 
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 pre- 
dominantly 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 significance 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 com- 
monly enumerated. 
We have, then, a number of systems of components each 
of which is defined structurally by similarity of peripheral and 
1 Presidential Address delivered before the Ohio State Academy of Science, 
Nov. 27, 1903. 
