THE AMYGDALA IN AMPHIBIA 245 
upon an inadequate appreciation of the underlying physiological 
principles involved. It is generally recognized that the analysis 
of the vertebrate nervous system in terms of the physiological 
modalities of the related peripheral end-organs has greatly clari- 
fied an obscure field. The detailed application of this method 
of attack is the distinctive contribution of the so-called American 
school, beginning with an adequate analysis of the functional 
components of the peripheral nerves and carrying this analysis 
more and more deeply into the intricacies of the higher correlation 
centers. 
The first generalizations to be derived from these studies 
(Strong, 95) brought out in sharp relief the fundamental nature 
of the distinction drawn by some of the early English physiologists, 
notably Bell and Gaskell, between the somatic and visceral 
systems of nerves, a conception later employed with brilliant 
results by Sherrington. 
This method of analysis has tones the central nervous 
system as helpfully as the peripheral, and its value in the fore- 
brain is not less than in the medulla oblongata. In fact, the 
tardy progress in the comparative morphology of the forebrain 
has been due chiefly to lack of exact knowledge in just this field, 
to ignorance of just what peripheral systems are represented 
in the higher correlation centers of the various animal types 
under investigation. Before we can reach final conclusions 
regarding the origin of the cerebral cortex we require much 
more detailed information regarding the connections of the pre- 
existing subcortical mechanisms of the forebrains of critical 
types. This applies especially to the centers of correlation 
between olfactory and non-olfactory systems. 
What names are applied to these systems is a relatively unim- 
portant matter, but it is necessary to bear in mind that the olfac- 
tory system itself is a complex in which visceral (interoceptive) 
and somatic (exteroceptive) elements are always present. To 
deny or ignore this dual nature of the sense of smell is to close 
the door to further progress. 
The olfactory apparatus, whatever may have been its primitive 
physiological character, has in fishes (as in most higher verte- 
