1885.] The Relations of Mind and Matter. 945 
over the brain fibers, on the same principle as external energy 
penetrates to the mind over these fibers, In this view the mental 
organism has a space extension, equivalent to that of the cere- 
brum, and each region bears a relation like that of external 
nature to every other region. 
The vividness of consciousness seems closely related to the 
degree of disturbance which it produces in the conditions of the 
mental organism. Energetic sensory impressions seldom fail to 
arouse consciousness, even if the mind is otherwise active. Less 
energetic ones may fail under such conditions. It is not unusual 
to discover that impressions have been unconsciously received 
during a period of mental abstraction. Possibly the movement 
of thought processes during unconsciousness is due to the small 
volume of energy engaged. An important fact, in this connec- 
tion, is that unusual impressions arouse the consciousness more 
quickly and vividly than usual ones, The mind seems to become 
dulled to a sensation when it has become habituated to it. With 
every repetition of any special current of energy it seems to 
create less disturbance in the mind. This may be partly due, if 
the sensation is one to which immediate motor response is requi- 
site, to the drafting off of part of the energy to the muscles, But 
even where this is not the case, and the impression is made 
wholly on the mind, its intensity diminishes with repetition, while 
all unusual sensations at once arouse active consciouness, Usual 
ones can only regain their original intensity of influence by 
an increase in their vigor. It would appear as if the vividness of 
consciousness depended upon the degree of change produced by 
a sensation in the mental conditions, and that each habitual sen- 
Sation found accordant mental conditions, and therefore feebly 
affected the mind, while every new one produced a degree of 
change in accordance with its degree of rarity. 
There is good reason to believe that every sensation that 
reaches the mind, however frequently repeated, is capable of 
awaking consciousness, and that only the completely reflex men- 
tal currents are absolutely unconscious. Thus certain tastes and 
Sounds may be received with full consciousness an indefinite num- 
ber of times. Yet with this rule the other holds good that an 
unfamiliar sensation most vividly arouses consciousness, and that 
all sensations less sharply affect the attention as they grow famil- 
iar. In all cases of the kind in which a sensation is seemingly 
