723a 
nature of the mind.* But no doubt his fears 
are unfounded ; for if we hold that a connec- 
tion subsists between soul and brain so intimate 
that every change in either affects the other 
more or less, surely the strongest inducement 
is held out for the minutest investigation of 
the organ which can exercise so wonderful an 
influence on the immortal part of our nature. 
I would, then, lay it down that the 
fanction of the brain is to generate the nervous 
foree, and that that force affects the soul and 
excites its action for the developement of mental 
phenomena. On the other hand, the action of 
the soul affects the brain, exciting it to the de- 
velopement of nervous force, and directing that 
force for the production or regulation of other 
cor phenomena. 
‘aking this view of the nature of the mind, 
and of the relation of mind and body, we may, 
with advantage, arrange the principal mental 
states into two classes, according as they are 
preceded by certain states of body, or as they 
precede and are capable of exciting certain 
States of body. 
' In the first class I would place sensation, 
and such mental states as are immediately asso- 
ciated with or produced by sensation, as the 
emotions and the i = this class I 
would likewise refer that iar power which 
is, with the highest probability, exercised by 
the cerebellum, and to which we must give the 
name of balancing or coordinating power. It is 
a power which, like the emotions and passions, 
is exercised without any previous train of 
thought or intellectual process, and seems sim- 
ply to be evolved as an immediate consequence 
of certain sensations, which are developed un- 
der the influence of impressions made upon 
the organs which are to be submntted to its 
regulation. Thus, in locomotion, the exercise 
of the muscles produces the sensation upon 
which the evolution of this mental power de- 
pends, which reacts upon the same muscles 
with an intensity proportionate to the exciting 
impulse. In the exercise of this power there is 
much analogy with the ordinary reflex acts ; but 
while the latter are purely physical in their 
nature, the former may be clearly shown to be 
mental. The proofs of this are derived, 1, from 
its being never accomplished without conscious- 
ness; 2, from its being always associated with 
volition ; 3, from the curious differences in the 
mode of its exercise in different individuals, 
according to differences of mental and physical 
constitution, one man being and precise 
in all his movements, another awkward and 
clumsy; 4, from the marked improvement 
which may be effected in it by instruction and 
dul ted tice. 
in ened oe I would place volition 
and attention. In these the mind has clear- 
ly the initiative, and is capable of inducing 
certain states of body, either to move certain 
organs (voluntary motion), or to concentrate 
one or more of the inlets of sensation upon 
some external objects (attention). The power 
* Wizan on the Duality of the Mind. Lond., 
44, 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
of abstraction, imagination, and all purely in- 
tellectual processes, are obviously associated 
with these. 
The symmetrical disposition of the parts of 
the encephalon on side of the median 
> has been recognised by all anatomists. 
his symmetry is so complete on we 
with correctness, s two brai 
Nani cad left brain, Esch are caine 
each other by transverse commissures. The 
right brain corresponds exactly with the left, 
just as much as the right eye corresponds with 
the left. This doubleness of the brain, no 
doubt, accords curiously with the double 
ness of all the organs of sense, and very pro- 
bably is rendered necessary by the existence of — 
the double set of inlets to sensation. It is” 
remarkable, however, that a symr : 
of the convolutions is not found in the hig 5 
races of mankind, and in individuals of high 
intellectual powers; and that the greater the 
mental power, the less symmetrical are the 
convolutions. In the inferior races, on ~ 
other hand, as Tiedemann has well shown, 
symmetry of the convolutions is exact. 
Upon the proved existence of two brains, as 
thus explained, Dr. Wigan, adopting the mat 
rialist view of mental phenomena, re: 
theory that the mind is dual; that we hk 
two minds; that each brain performs its 
mental functions, which are in perfect harmony. 
if the two brains harmonise in quality, structun 
and action. 
it cannot be doubted that two brains, 
symmetrical in structure, must have a t 
mount symmetry of function, if I 
allowed the expression ; and that, the: 
order to insure harmony of action b 
them, and to prevent the actions of one fi 
interfering with or neutralising those of | 
other, some such organic connection b 
them is n as that which exists betw 
the two retina, and which converts the st 
rate and im some degree dissimilar physi¢ 
impressions made on each of them into oI 
sensation. 
And as any interference with the 
conditions necessary to secure si 
with two eyes produces double vision, so 
not unreasonable to expect that an anak 
imperfection in the organie union betwee 
two brains may occasion doubleness of 
impression and action. Such acon 
Dr. Wigan has ingeniously ted, 
the clue to the explanation of enol 
as states of double consciousness, delus 
irregular volitions, and some forms of insa 
and, if fairly worked out by physiological 
chologists, may solve other obscurities 
nected with the phenomena of the 
While, therefore, I admit that = Fac 
interest and value attach to Dr. Wigan’s 
respecting the action of two brains, Tal 
prepared to infer the existence of two ™ 
from that of two brains; no more thal 
can assume a duality of our visual sem 
from the existence of two eyes. The 
cases, indeed, are strictly analogous. 1 
organic change in each retina develope: 
= 
