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substances, — the one, a material substance, consisting of 
elementary atoms ; the other a spiritual substance, consisting 
of feelings, thoughts, and emotions; yet they stand in intimate 
and close connection with each other. 
They are so connected that, when the functions of the mate- 
rial organism are interfered with, the phenomena of the mental 
factor are deranged. If the body or the mind, or both, be in 
a diseased state, there maybe delusions.* But the connection 
between mind and brain is a mystery. The w r hole relations 
of the two are inconceivable to us. How they act and re-act 
on each other we cannot tell. The gap between them is wide, 
and the passage unthinkable. 
Mind is not conscious of its dependence on material organs ; 
and is not enchained in any special organs. But as certain 
parts-}- of the nervous and cerebral centres are more con- 
nected with one set of sensations than another, so certain 
parts of the same centres may be more connected with one 
train of thought than another. 
“ The state of the visceraj has an influence on our psychical 
tone ; and, again, our feelings influence our organic functions.” 
But mens sana and corpus sanum , though desirable, are not 
“ essentially correlatives,” as there is often a mens sana con- 
nected with a corpus insanum . 
Though the functions of the brain organism are connected 
with the phenomena of mind, and a certain affection of the 
nervous system produces a certain affection of mind, yet 
philosophers maintain that mental events have nothing in 
common with the molecular movements of the nerve centre. 
They cannot be reduced into one another; yet the stroke 
which paralyzes the brain may paralyze reason, memory, and 
will. 
Sensation . 
What do the brain and nervous system, as an organism, do 
for the mind ? Through the organs of sense they furnish the 
mind with those feelings called sensations. 
“ A sense is the capacity § of the mind for a distinct class of 
sensations in connection with bodily organization ” ; and a 
sensation is an affection of the mind arising from physical 
impressions on some one of these organs. But the transi- 
tion from the impression on the organ of sense to the mental 
feeling is a mystery to which we have no key. 
We have no sensations which do not come to us through 
* Page 124. 
f Page 123. 
X Page 121. § Cairns’s Logic, p. 9. 
