72ic 
ologists to the existence of a power in the 
nervous centres which no doubt exercises a wide 
influence on the phenomena of living creatures ; 
and yet it seems extraordinary that neither of 
these physiologists in their earlier writings 
should have made the slightest allusion to 
Prochaska, who had offered a more precise 
and more comprehensive, and, as I hope to 
show, a truer explanation of the phenomena 
than either of them. 
I shall here cite various facts, in addition 
to those already adduced, which unequivocally 
demonstrate that a power exists in the cord of 
exciting movements in parts which receive 
nerves from it, by changes occurring in its 
substance, which may arise there from some 
modification of its nutrition developed in the 
cord itself, or be excited by a stimulus brought 
to act upon it by afferent or sensitive nerves. 
But more than this: the cord has the power 
of reflecting the change wrought in it by im- 
pressions conducted to it into adjaceut sensi- 
tivé nerves, thus creating a large class of reflex 
phenomena under the name of reflex or radia- 
ting sensations. 
When a stimulus is applied to the spinal 
cord, either directly or through the medium 
of afferent nerves, the actions excited by it are 
generally limited to. those parts which derive 
their nerves from that segment of the cord which 
has received the stimulus. In some instances, 
however, parts supplied from other and even 
distant segments are thrown into action. Thus 
irritation of one leg may cause movements of 
one or both of the upper extremities ; the intro- 
duction of a catheter into the urethra will some- 
times give rise to forcible contractions of the 
muscles of the lower extremities or even of all 
the limbs. These effects are due, no doubt, to 
the extension of the stimulation in the cord be- 
yond the point first acted ee ; and they may 
be regarded as proofs that that peculiar state of 
physical change which nervous stimulation can 
excite in a centre may be propagated in the 
spinal cord upwards, downwards, or sideways, 
from the seat of the primary stimulation. 
This fact was pointed out first, so far as I 
know, by Dr. M. Hall, who regards it asa 
eke of the cord in its normal state. This, 
am inclined to think, is an error; I believe 
it to be a property of the cord, only when its 
polarity is exalted. It is, however, an important 
property, and we shall, by-and-bye, make use of 
it in considering the mechanism of the various 
actions of nervous centres. Meantime we may 
obtain, from examining into the morbid states 
which are apt to arise in the spinal cord and 
in other parts of the cerebro-spinal centres, in- 
teresting confirmation of it. 
A wound in the sole of the foot or ball of the 
thumb, or in some other situation favourable to 
the maintenance of prolonged irritation, is ca- 
pable of exciting a particular region of the 
cord, from which the state of excitement spreads 
so as to involve not only the whole cord, but 
part of the medulla oblongata also ; and in this 
state a large proportion of the motor nerves 
participate, so as to induce tonic contraction of 
the muscles they supply. This is the rationale 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
of the developement of that fearful malady 
called ¢e¢tanus. It consists not in an inflamma- 
tory condition of the cord or of its membranes, 
nor in congestion of them, but simply in a 
state of prolonged ee excitement, the 
natural polar force of the centre being greatly 
exalted and kept so by the constant irritation 
propagated to it by the nerves of the wounded 
part. Intestinal irritation is capable of, pro- 
ducing a similar condition, which, if the irrita- 
tion have not been allowed to remain too long; 
may be speedily removed by getting rid’ of the 
irritating cause. The following case illustrates 
this: an unhealthy looking girl, about, fifteen 
years of age, was brought into King’s College 
Hospital suffering from severe tovie spasms of 
the muscles of the spine and lower extremities. 
The spasms were so powerful as to produce 
successive paroxysms of opisthotonos, during 
which the trunk became bent like a bow, so that 
the patient rested on her occiput and on her 
heels. This state was speedily removed bythe 
use of a large purgative clyster containing tur- 
pentine, which brought away a large number of 
ascarides from the rectum. re aly 
In cases of paraplegia from disease of the 
spinal cord, the paralysed parts, are frequently 
troubled with cramps and_ startings occurring 
chiefly at night, and preventing sleep and ocea- 
sioning great distress to the . patient., 
are very often traceable to intestinal disturb- 
ance, the presence of irritating matters, which, 
stimulating the mucous membrane, through its 
nerves excite the spinal cord, and thus produce 
these involuntary movements. seer pl 
The rigid and contracted state of the muscles 
of paralysed limbs, which fiiequently accompa- 
nies red softening of the brain, arises. from. 
propagation of the excited state of the diseased 
part of the brain to that portion of the Fern , 
cord which is connected with it, and from whie 
the nerves of the paralysed parts arise, thet se 
nerves likewise participate in. the irritation of — 
the cord, and thus keep the muscles. ina state — 
of continued active contraction. There is no~ 
organic lesion of the cord in these cases; its 
state of excitement is dependent on the cerebral 
irritation, and disappears if the latter yields to 
the influence of remedial measures. if 
To a similar extension of cerebral irritation, 
although of a much briefer duration, the con- 
vulsions of epilepsy may be attributed. Th 
brain becomes the seat of irritation, and 
spreads to the whole or a part of the spi 
cord and to the nerves which arise from it. In 
many instances of epilepsy the convulsions aré 
limited to one half of the body, and this is espe- 
cially the case where a chronie lesion exists im 
the brain and forms a focus of irritation, whieh 
is propagated only to one half (the opposi 
the cord. 
Some substances exert a peculiar influence 
upon the spinal cord and throw it into a st 
of considerable polar excitement... Strychr 
is the most energetic substance of this class. 
a certain quantity of this drug be injected into 
the blood or taken into the stomach of an ami 
mal, a state of general tetanus will qui 
ensue, sensibility being either unaltered or som 
