PRESIDENT’S ADDRESS—SECTION J. 157 
retraction possessed by the gemmules or lateral processes. In 
the condition of extension they approach so near to those of 
other dendrites that the energy generated in the neuron of the one 
passes into the fibres of the other. If all the gemmules are in a 
state of extension, any energy liberated will be so diffused over 
the whole dendritic processes of the cortex as to produce a 
generalised co-ordinate functionising, producing but little effect, 
and which is probably the condition of natural sleep. During 
active mentalisation it appears necessary that the motility of 
these gemmules should be at their greatest, so that upon a suffi- 
ciently strong stimulus liberating energy, a certain number of 
them retract, leaving only a few in a state of extension. The 
result is a distinct action in a given direction which may 
rise into consciousness, and we feel that we have made an 
effort or controlled our mental processes. This making of 
efforts is exhaustive, and soon wearies the neurons, and deadens 
the motility of the gemmules. We then experience the feeling 
of being tired. This expenditure of force being wasteful from a 
physiological economic point of view, we find that the necessity 
for it is reduced to a minimum as quickly as possible. This is 
brought about by paths of functioning becoming more organised 
or altered, that is, they lose their gemmules, and the fibres 
become encased in a non-conducting material which saves the 
necessity of causing the retraction of the gemmules when it is 
desired to prevent the diffusion of the impulse to the contiguous 
dendrites. Only the functioning gemmules remain what is 
called “naked.” As a result a train of functioning is estab- 
lished, and requires a much weaker stimulus to set it in action 
than in the earlier stages when a great effort was necessary, be- 
cause the possibility of diffusion is lessened. In fact, the path 
thus formed for certain impulses becomes so easy for them to 
travel along that no feeling of conscious effort is evoked, and the 
action is then said to be automatic. Most of our mentalisation 
is of this character, and in thinking we are only conscious of 
some of the ultimate resultants from the invading of new tracts 
by terminal fibrils, which still retain their naked protoplasm so 
as to allow of impulses being transmitted from one to the other. 
It is this condition which makes progressive education a pos- 
sibility. 
Such being the rough general mechanism, the question 
of the conditions necessary for effective functioning may be 
briefly considered. As the dendritic processes are extensions of 
the neurons, and as on these processes depend the possibilities 
of associated action, the proper nutrition of the neuron must 
be of primary importance. The neuron as a portion of the 
organism will be well nourished or otherwise in common with 
the other tissues of the body; and in proportion as other parts 
are functioning effectively so will the physiological activities of 
