722¥ 
neither pain nor disturbance of motion. Even 
the electric current ed through them pro- 
duces no sensible idivet: (Matteucci). We are 
led, therefore, to the conclusion that these fibres 
have endowments quite distinct from those of 
sensitive and motor nerves, (a fact, by the 
way, quite irreconcileable with the doctrine 
which makes the brain the concourse of these 
fibres,) and that they are internuncial between 
parts which are beyond the immediate influence 
of the ordinary physical agents, and which 
have no direct connection with muscular organs. 
The proper stimulant of these fibres is the 
mind on the one hand, or the nutrient changes 
in the brain on the other. But, under the 
influence of a continued morbid irritation, they 
may excite either pain or convulsion, or both, 
as is frequently the case in disease of the 
cerebral meninges ; this, however, is effected 
through a change produced in the corpora 
striata and optic thalami, and propagated thence 
to the origins of motor and sensitive nerves, or 
through irritation of the nerves of the meninges, 
which affect the centres of motion and sensa- 
tion, just as the nerves of other parts do. 
The experiments of Flourens and of Hertwig 
show that removal of the cerebral hemispheres 
produces a state of stupor, and, to use Flourens’ 
expression, as it were condemns the animal to 
perpetual sleep, but deprives it even of the fa- 
culty of dreaming. There is, however, no para- 
lytic state produced by these mutilations. It is 
evident, then, that the effect of these experi- 
ments is psychical, and it may be adduced as 
confirmatory of the view which associates the 
functions of the cerebral convolutions with the 
operations of the mind. 
Pathological anatomy affords interesting con- 
firmation to this view. Inflammation of the 
membranes of the brain, more especially of 
the pia mater, is invariably attended by dis- 
turbance of the mental faculties, as manifested 
by more or less delirium. It appears that 
any material alteration of the circulation in 
the grey matter of the convolutions is capa- 
ble of giving rise to delirium; in the in- 
stance above quoted, the circulation in this 
part is affected in consequence of the inflam- 
mation of the pia mater, the bloodvessels of 
the one being distinctly continuous with those 
of the other; but in other instances of violent 
delirium, such, for example, as delirium tremens, 
the vesicular matter of the convolutions is found 
after death to be bloodless, as if its wonted 
supply of blood had been cut off or abstracted 
from it. We find this state in the delirium 
after great operations, after puerperal floodings, 
in the delirium of rheumatic fever, and in that 
of gout, and likewise in that which occurs in 
the more advanced stages of fever. 
We learn from the most trustworthy reports 
of the dissections of the brains of lunatics that 
there is invariably found more or less disease of 
the vesicular surface and of the pia mater and 
arachnoid in connection with it, denoted by 
opacity and thickening of the latter with altered 
colour or consistence of the former. 
From these premises it may be laid down as 
a just conclusion that the convolutions of the 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
1 
| 
brain, in other words, that vast sheet of vesicular 
matter which crowns the convoluted surface of | 
the hemispheres, constitute the centre of intel- 
lectual action, as distinguished from the centre 
of volition and the centre of sensation (corpora 
striata and — thalami). It is essential to the — 
perfection of cerebral action that these centres 
should be connected, and that the centre of in- 
tellectual action should be capable of exciting 
or of being excited by the centres of volition — 
and sensation. This connection and mutual — 
influence is effected through the innumerable — 
fibres which pass from the one to the other. 
To determine the precise connection which 
exists between the mind and the brain is beyond — 
the reach of our means of observation and = 
periment. All we are justified in affirming is 
that the mental acts are associated with this por- — 
tion of the brain, which I would call the centre 
of intellectual actions ; and that the integrity 
of this is 0 to the perfect exer-— 
cise of the mind ; that, in the language of Cu- 
vier, this centre is the sole receptacle in which 
the various sensations may be as it were con- 
summated, and where all sensations take a 
distinct form and leave lasting traces of their 
impression, serving as a seat to memory, @ 
adele by mnesind a which the animal is fur- 
nished with materials for his judgment. = 
The actions of the convoluted surface of thi 
brain, and of the fibres connected with it, be’ 
altogether to the class of mental nervous acti 
that is, they either excite or are excited b 
mental change. The physical changes in the 
parts give rise to a corresponding manifestatic 
of ideas, and every thought is accompanied ‘ 
a change in this centre. Modifications in 
nutrition, or interruptions to it, uce ¢ 
responding effects on the mind. increas 
activity of nutrient change causes a rapid d 
velopement of ideas, which, being generally 
controllable by the will, and therefore 
rected, assumes the form of raving or deliri 
The shock of concussion so far check 
organic changes of the vesicular surface, ¢ 
perhaps also of the fibrous matter, as to i 
rupt for a time those conjoint actions 
mind and the brain which are necessary 
perfect consciousness. The condensation 
the substance of the hemispheres, whic 
produced by an apoplectic clot, or by 
effusion of some other foreign matter, prey 
a similar consent of action, and thus gives 
to the phenomena of coma, a state in whic 
mental nervous actions are destroyed or 
pended, and which, if continued long ent 
will annihilate the physical nervous ac 
likewise. i 
It will be observed that, in this descrip 
the workings of the mind are not view 
mere functions of the brain. The term: 
expresses the mode of action of the Sou 
entity which both reason and revelation é 
us is essentially different from the Body,* I 
incorruptible and indestructible, in t 
in which we suppose that both corruption a 
destruction may affect material things. — 
* Ens incorporee prosapia, Prochaska. . 
