1885.] The Relations of Mind and Matter. 763 
checked at the ganglion. And another result of great importance 
is that every such unusual impression, thus partly or wholly 
checked in its course, produces the effect of memory at the gan- 
glion. Thus a record is laid up in the memory of every unusual 
impression, which is vivid at first but grows less and less so with 
every repetition of this impression. Finally, when a particular 
sensation grows habitual it may cease to affect the memory record. 
It has already made a deep impression there, and it subsequently 
is received with less and less consciousness of its existence. If 
it passes on to the muscles it may do so utterly without affecting 
consciousness, or become completely reflex. 
As centralization proceeds it seems probable that all such un- 
usual impressions are directly transmitted from the inferior to the 
central ganglia. In this direction there appears to be the freest 
channel of conduction for sensory currents. Usual impressions 
may have opened direct lines to the muscles, but unusual ones 
pursue a more open and general channel leading towards the 
central organ, in which the final duty of discrimination is exer- 
cised. And as a consequence, in the higher vertebrates the main 
center of reflex action seems to have become the ganglia at the 
base of the brain. In the insects the ganglia of each section 
seem to exert an active reflex function. This has largely ceased 
to be the case with the spinal ganglia of man, whose main reflex 
center is the cerebellum and the contiguous ganglia. 
In all the higher Vertebrata a nervous organ has been devel- 
oped which does not seem to exist in the invertebrate animal 
world. This isthe cerebrum. It is a special gangliar organ de- 
voted solely to the duty of memorizing, and one in which con- 
sciousness has become centralized. In the ant, the most intelli- 
gent of invertebrate animals, there is no apparent differentiation 
in the head ganglion. It is a single organ, centering in itself 
duties of reflex and instinctive action, and of memorizing. In 
the highest animals these duties have become separated. The 
inferior brain ganglia apparently possess the function solely of 
reflex action, if we may view as a constituent part of this function 
the diversion of unusual impressions upward to the cerebrum. That 
is to say, they have lost all power of checking the flow of nerve 
energy. Memorizing and psychical action seem confined to the 
cerebrum. And intermediately sensations of increasing frequency 
grow partly reflex and partly affect the cerebrum without calling 
