40 
irritability is diminished, and at length becomes 
extinct, from its source being cut off. 
We may further deduce, from the facts whith 
have been detailed, that the spinal marrow and 
not the cerebrum is the special source of the 
power in the nerves of exciting muscular con- 
traction, and of the irritability of the muscular 
fibre; that the cerebrum is, on the contrary, 
the exhauster, through its acts of volition, of 
the muscular irritability. 
As a further deduction from the same facts, 
we may infer the diagnosis between cerebral 
and ci paralysis: mere cerebral paralysis is 
attended by augmented irritability, w 
spinal paralysis is that which is attended by 
diminished irritability. This fact will prove 
useful in many obscure cases. 
Having thus cleared up the physiological 
question, I proceed to the application of the 
principle to pathology ; and I may here observe 
that there is a whole series of phenomena which 
admit of explanation by its aid. 
And, first, the exception to the rule of aug- 
mented muscular irritability in paralytic limbs, is 
obviously dependent upon its existing in the 
cases of paralysis from the severed influence of 
the spinal marrow, as distinguished from those 
arising from the severed influence of the cere- 
brum merely. 
Secondly, we understand at once why the 
influence of strychnine is first and most seen in 
cerebral paralysis in the paralytic limbs. 
But there are still some other points which I 
must bring before the notice of the reader. 
The first of these is the influence of emotion 
in | pe limbs. 
he second is the similar influence of certain 
acts of respiration; as yawning, sneezing, 
coughing, &c. 
The third, the similar influence of the tonic 
power. 
It must have occurred to us all to observe 
the influence of surprise or agitation on the arm 
and hand, and perhaps on the leg, of a patient 
long affected by hemiplegia, whilst the limbs 
of the healthy side remained unaffected. In 
this case the influence of the emotion is, like 
that of strychnine in the case formerly discussed, 
exerted equally upon the limbs of both sides; 
but it is the muscles of the paralytic limbs 
which are most irritable, most susceptible of 
the stimulus ; it is, therefore, these limbs which 
are most convulsively affected. 
The same phenomenon is not observed in 
plegia, because the influence of the emotion 
is cut off from the affected limbs. 
Case 1.—I was called to a patient a short 
time ago, affected at that moment with bron- 
chitis. He was forty-three years of age, and at 
the age of twenty-four had been seized with 
hemiplegia. Recovering from the immediate 
danger of the attack, he remained hemiplegic, 
searcely regaining the use of the hand and arm 
at all, and only partially that of the leg. 
Whenever this patient is excited by meeting 
an acquaintance, or in any similar way, he has 
a little strabismus, and the hand and arm are 
contracted and convulsed in the most extraor- 
dinary manner: whenever he coughs, the leg 
IRRITABILITY. 
is thrown involuntarily upwards. The arm i 
severed, as it were, from volition, but affeete 
by emotion. 
Similar facts have been observed in t 
to the influence of certain respiratory acts, 
especially those of yawning, sneezing, &c. 
Dr. Abercrombie details the following int 
resting case in a note to the late Mr. Shaw. 
“ T think the following case will be interes 
ing to you and Mr. Bell. I had some tim 
ago under my care, a man affected with hemi 
plegia of the left side; the palsy complete, will 
out the least attempt at motion, except um 
the following circumstances : he was very muc 
affected with yawning, and e time — 
yawned the paralytic arm was raised up, with 
firm steady motion, until it was at right angle 
with his body (as he lay in bed on his back 
the fore-arm a little bent inwards, so that hi 
hand was above his forehead at its great 
elevation. The arm was raised steadily dui 
the inspiration, and when the expiration bega 
seemed to drop down by its own weight, wit 
considerable force. He continued liable to 
affection for a considerable time, and it cease 
gradually as he began to recover the natura 
motion of the limb.”—That is, as I concludi 
as the state of augmented irritability was te 
moved by the returning acts of volition, ~~ 
Not less interesting are the effects of 
tonic power. In cases of hemiplegia of lon 
duration, the paralytic limbs, but especially 
arms and hands, are drawn into a state 0 
chronic, rigid, contraction. This phenomeno 
is owing to the principle of tone constantl 
acting upon muscles now ing augmentet 
irritability, whilst they are never, or rare 
relaxed by acts of volition. . 
A similar effect is seen in idiots born with 
atrophied cerebrum: the influence of voli 
is wanting; that of the spinal marrow, the 
source, at once, of the tone and of the irrita 
bility of the muscular system, is in constan 
action, and induces chronic contraction, a 
effect which must, however, be distinguisher 
from that of spasm, which is excited imme 
diately by some disease of the spinal marrot 
itself. ta 
I may now resume the subject of the actio 
of strychnine on paralytic limbs. It is obviot 
that the generalization of M. Fouquier, M. Sé 
galas, and others, that the chnine atta 
the paralytic rather than the healthy limbs, wa 
too hasty. This is only true in those cases « 
paralysis in which the muscles still remain i 
nervous connexion with the spinal marrow; tl 
opposite result is observed in those other case 
in which such connection between the musel 
and the spinal marrow is intercepted. : 
I would here make another observation. The 
arms and hands, generally speaking, are mor 
under the influence of the cerebrum than th 
lower extremities; and these, on the othe 
hand, are more under the influence of th 
spinal marrow than the arms and hands. TI 
superior extremities are more and more fre: 
quently affected by hemiplegia than the infer 
these are more influenced by tetanus, b 
strychnine, &c. than the former, a fact whit 
ia 
