118 KANSAS CITY REVIEW OF SCIENCE. 
the same, except the molecular arrangement. When the impression ceases, the 
cells cease to vibrate, and obtain a period of rest which is essential to memory. 
It will be noticed that the vibration of a cell is clear to the mind, because it 
acts in its entirety, rest, and vibrates again to the same impression ; each 
vibration fixes permanently its peculiar movement, and we have a cell which 
vibrates to no other impression, and the result is a memory-cell. This is much 
better than the residuum theory which leaves a residuum after every cell vibration 
and eventually a permanent one. 
When an impression is received upon the retina, tympanum, tongue, fingers, 
or olfactory bulbs, jit is conveyed by proper nerve filaments to cells in the gray 
matter of the brain. These cells vibrate from excitation, and undergo a change, 
say, that of molecular arrangement. If this impression is repeated often enough 
the molecules are permanently changed and we have memory-cells and remember 
the impression. If, on the other hand, the impression is made but once, and 
then not violently, the cells assume their first condition and we forget the impres- 
sion, it passes from our mind. In this connection let me say that in the true 
sense, we do not see an object, hear a sound, feel a substance, smell an odor, or 
taste edibles; we simply become conscious of the impression, when they irritate 
to vibration the cells in the gray matter. These impressions cause different cells 
to vibrate the same to the same excitations, which allows differentiation, and 
memory is the result. If different cells responded to the same impression, there 
would be no permanency, consequently no cognition, 
Why do the same cells vibrate to the same impression? The most plausi- 
ble explanation is molecular change. If we strike a bar of steel upon the end 
with a hammer, we can produce a magnet. The blow causes a change of mole 
cules in the steel, and polarizes them. Whether the molecules of a cell are 
simply changed, or polarized, is hard to determine, but that some change takes 
place by vibration is evident from the fact that we remember more easily where 
the impression is received many times. 
If the molecular theory is correct, and every substance is composed of mole- 
cules, the whole body cells in the gray matter would be no exception 
Some men of learning say, that the molecules of the body are polarized in health, 
and when disarranged disease is the result. If this is true, and nervous force 
electricity, and the brain the battery, why not say that the change in a memory- 
cell is molecular ? 
Why does the same cell vibrate to the same impression ? Force or motion 
travels in the direction of the least resistance. When an impression is carried 
along a nerve fibre, there is a certain amount of resistance, and every impression 
weakens its power to resist, and each succeeding impression travels along the 
fibre which is attuned to it and has the least resistance. If the same impression 
is carried on the same nerve fibre, it must necessarily reach the same cell, whith 
vibrates according to its molecular change and we become conscious of the im- 
pression. I would, in this connection, say that repeated impressions are not 
always necessary to produce a memory-cell. A sudden violent excitation will 
