542 
David H. Dollev 
chanism and in purpose, there is no other resonrce. Anatomically, 
specialization in tlie nerve cell is the accomplisliment of the forination 
of chromatin, which is the work of the cell, more rapidly and within its 
limits more efficiently. Its actual differences of grade, the possession 
of these qnalities in greater or less degree, would in terms of this con- 
creto conception be placed entirely npon the fundamental Chemical basis, 
which no one donbts is the ultmiate and predominant one in the matter 
of vital dynamics. The morphological changes are put in theii- proper 
secondary relation and more light is thrown upon the way Chemical re- 
actions display themselves in striicture. 
With this the inherent nature of its differentiation, it foUows that 
diversity and complexity of fimction, as manifested in the crayfish, 
are essentiaUy due to the diversity and complexity of the associational 
neurons intercalated between the primal ones, which was the ground taken 
in the analysis of cell types. The primal sensory and motor ceUs, common 
as they are to aU ganglia, playing imcpiestionably the predominant role 
and among themselves on an identical plane in mechanism and in the 
piu’pose accomplished by the mechanism must conserve all varieties of 
Sensation and motion. The ränge of fimction is a matter of inter-ro' 
lation and connection between neurons brought about by association 
cells and not one of varying and peculiar cellular reaction. To the extent 
to which the unity of mechanism is universal, this can be applied uni- 
versaUy. That association is the predominant factor in the evolution 
of fimction is a thing of fundamental knowledge as regards itself. But 
the evidence presented from the side of the nature of the reaction of 
the nerve ceU in this and higher animals is interpreted as pointing to the 
absolute elimination of inherent differences in specific cellular powers as 
not at aU demanded in explaining the most diverse fimction. Differ- 
entiation is regarded as a matter of relative quality, not one of mode 
of reaction. Between higher and lower ceUs there are differences, Chemical 
in nature, so that the former work more rapidly and relative to that more 
efficiently, but neither accomplishes in its ultimate analysis any more 
nor any less than the other. 
While it is a long step to the exact knowledge stated in Chemical 
formiüae, meanwhile the morphological c-xpression of the reactions may 
be saiely expected to extend to a far-reaching Interpretation of the re- 
lation of cellular dynamics to the outward fimctional powers and limita- 
tions of the individual. In this conception of the dynamics of the nerve 
cell the wiiter is fully aware that certain structural elements, perhaps 
weighty, are apparently neglected and will have to be brought in correla- 
