Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 3: Ins-Pla
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29464/790/
722q 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
but to the vigour and health of the body also ; 
that to ensure the full developement of the 
mens sana we must secure the possession of the 
corpus sanum. 
Certain diseases are evidently associated 
with disturbed or excited states of emotion. 
In such cases, the nerves most affected are 
those connected with the mesocepbale and 
medulla oblongata, denoting an excited state of 
these portions of the encephalon. Of these 
diseases the most remarkable are hysteria and 
chorea; both of which may be induced either 
by a cause acting primarily upon the mind, or 
by functional disturbance of the body, as de¬ 
ranged assimilation, in persons of a certain 
character of constitution. In hysteria, the 
globus, the tendency to cry or laugh, the dis¬ 
turbed breathing, the variously deranged state 
of the respiratory acts, all denote affection of 
most, if not all, the nerves coming from these 
segments. In chorea the frequent movements 
of the face and eyes, the peculiar and very 
characteristic mode of protruding the tongue, 
the impaired power of articulation, are depen¬ 
dent on an altered state of that part in which 
the portio dura of the seventh pair, the third, 
fourth, and sixth, and the ninth nerves are 
implanted. In both diseases the principal 
central disturbance is in the mesocephale ; and 
this may be caused either by the direct in¬ 
fluence of the mind upon it, or by the propa¬ 
gation of a state of irritation to it from some 
part of the periphery. Chorea, even of the 
most violent and general kind, is very commonly 
produced by sudden fright; and it is well 
known how frequently mental anxiety or ex¬ 
citement developes the paroxysm of hysteria. 
There is no part of the cerebro-spinal centre 
which appears to exercise such extensive sway 
over the movements and sensations of the body 
as this portion, the mesocephale, which may be 
regarded as the centre of emotional actions. 
Its influence extends upwards to the cerebral 
convolutions—backwards to the cerebellum— 
downwards to all the nerves of sensation and 
motion. Through its connection with the pos¬ 
terior horns of the spinal grey matter, it can 
excite the sensitive as well as the motor nerves 
of the trunk. Hence it is not to be wondered 
at that a highly disturbed state of this centre is 
capable of deranging all the sensitive as well as 
motor phenomena of the body and even the 
intellect. Hence we may explain the extra¬ 
ordinary movements in hydrophobia and ge¬ 
neral chorea, in both of which diseases this 
part of the nervous centre is doubtless affected. 
It has often been remarked how much more 
powerful are the voluntary actions when 
prompted by some strong emotion, than when 
excited only by an effort of the will. Rage, 
or despair, is able to magnify the power of the 
muscles to an incalculable degree. This may 
be due to the increased stimulus derived from 
the influence of the centre of emotion being 
conjoined with that of the centre of volition. 
The intimate connection of the olivary co¬ 
lumns with the grey matter of the cord, and 
through that with all the roots of the spinal 
nerves, illustrates the power of emotional 
changes upon the organic processes. How 
often does the state of the feelings influence 
the quantity and quality of the secretions, no 
doubt through the power of the nerves over 
the capillary circulation ! Blushing is pro¬ 
duced through an affection of the mind, acting 
primarily on the centre of emotion, and 
through it on the nerves, which are distributed 
to the capillary vessels of the skin of the face. 
The sexual passion must be ranked among 
the mental emotions. Like them, it may be 
excited and ministered to by a certain line of 
thought, or by particular physical states of the 
sexual organs. It seems, therefore, more cor¬ 
rect to refer this emotion to the common centre 
of all, than to a special organ—according to 
Gall’s theory; and it may be remarked, that 
great developement of this part of the brain is 
just as likely to produce great width of cranium 
in the occipital region as a large cerebellum. 
Of the functions of the cerebellum.—All ana¬ 
tomists are agreed in admitting, in the whole 
vertebrate series, (the amphioxus, perhaps, ex¬ 
cepted,*) the existence of a portion of the en¬ 
cephalon which is analogous to the cerebellum. 
This extensive existence of such an organ indi¬ 
cates its great physiological importance, as a 
special element of the encephalon. The ce¬ 
rebellum exhibits much difference both as re¬ 
gards size and complexity of structure in the 
different classes ; and although, upon the 
whole, it increases in its developement in the 
same ratio as the hemispheric lobes, it exhibits 
no constant relation of size to those parts. 
The large size and complicated structure of 
this organ in the higher vertebrate animals, 
and its distinctness from the cerebrum,—for its 
commissural connection with that segment of 
the encephalon is not extensive,—have excited 
the interest and curiosity of speculative physio¬ 
logists ; and, accordingly, we find no part 
respecting which a greater variety of hypotheses 
have been suggested, most of them being en¬ 
tirely devoid of foundation. The experiments 
of Flourens have, however, thrown more light 
on this subject than any previous observations ; 
and his hypothesis appears nearer the truth than 
any which has been proposed. 
The facility with which the cerebellum may 
be removed or injured, especially in birds, 
without involving the other segments of the 
brain, renders it a much more favourable ob¬ 
ject for direct experiment than them. A skil¬ 
ful operator may remove the greater part or the 
whole of the cerebellum without inflicting any 
injury on the hemispheres or other parts. 
Flourens removed the cerebellum from pi¬ 
geons by successive slices. During the removal 
of the superficial layers there appeared only a 
slight feebleness and want of harmony in the 
movements, without any expression of pain. 
On reaching the middle layers an almost uni¬ 
versal agitation was manifested, without any 
sign of couvulsion : the animal performed rapid 
and ill-regulated movements ; it could hear and 
* The observations of Quatrefages render it 
doubtful that even the amphioxus can be regarded 
as forming an exception. Ann. des Sc. Nat., 1846.
        

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