IRRITABILITY. 
_ I next repeated my observations upon a more 
extensive scale, at the St. Mary-le-bone and St. 
Pancras Infirmaries. There were two exceptions 
to the rule; whilst the numbers in which the 
phenomena as already described were observed 
_ were considerable. 
a These exceptional cases I shall notice parti- 
_ cularly hereafter. I must now remark that 
these observations seem, even more than those 
_ of Prochaska, Nysten, and Legallois, at vari- 
ance with the experiments of Professor Miiller 
_and Dr. Sticker. Before I proceed to discuss 
- this question, I must, however, detail some ex- 
_ periments of my own. 
| They were made on six frogs. I divided the 
_ Spinal marrow immediately below the origin of 
_ the brachial plexus ; and I removed a portion 
_ of the ischiatic nerve of the right posterior ex- 
_tremity. I had immediately, or more remotely, 
the following interesting phenomena. 
ist. The anterior extremities alone were 
moved spontaneously; both posterior extremi- 
ties remaining entirely motionless, when the 
animal, placed on its back, made ineffectual 
efforts to turn on the abdomen. 
_ 2d. Although perfectly paralytic in regard to 
Spontaneous motion, the left posterior extre- 
mity, that still in connexion with the spinal 
_ Marrow, moved very energetically when sti- 
_ mulated by pinching the toes with the forceps. 
_ 3d. The right posterior extremity, or that of 
_ which the ischiatic nerve was divided, was en- 
_tirely paralytic, both in reference to sponta- 
_ neous and excited motions. 
__ 4th. After the lapse of several weeks, whilst 
_ the muscular irritability of the left posterior ex- 
tremity was gradually augmented, that of the 
_ right was gradually diminished, phenomena ob- 
_ served when the animal was placed in water, 
through which a slight galvanic shock was 
_ passed accurately in the direction of the mesial 
plane. 
___In this interesting experiment we have, then, 
first the phenomena of loss of spontaneous mo- 
_ tion on removing the influence of the brain, the 
_ excited or reflex actions remaining; and the 
loss of these on removing the influence of the 
spinal marrow; secondly, in the case of mere 
cerebral paralysis, we have augmented irritabi- 
lity, and in that of the spinal marrow we have 
_ the gradual diminution of this property. 
] 5th. Strychnine being now administered, the 
_ anterior extremities and the left posterior extre- 
' mity, or that still in connexion with the spinal 
_ marrow, became affected with tetanus ; but the 
right posterior extremity, or that severed from 
_all nervous connexion with the spinal marrow, 
_Temained perfectly flaccid. 
__ 6th. Lastly, the difference in the degree of 
"irritability in the muscular fibre of the two 
_ limbs was observed when these were entirely 
_ separated from the rest of the animal. 
__ In a word, the muscles of the limb para- 
lysed by its separation from both cerebrum and 
spinal marrow, had lost their irritability; whilst 
those of the limb separated from its connexion 
with the cerebrum only, but left in its con- 
nexion with the spinal marrow, not only re- 
tained their irritability, but probably possessed 
ett 
39 
it in an augmented degree. The next question 
came to be,—Do these phenomena obtain in 
the human frame? _I visited a patient affected 
with hemiplegia, including paralysis of the face, 
and I passed a slight galvanic shock through 
two pieces of metal, of which one was placed 
over each cheek. The muscles of the paralytic 
side were most affected. 1 repeated the expe- 
riment with the same result. I now compared 
with these, two cases of injury of the facial 
nerve, passing the galvanic shock in the same 
manner, through the fibres of the orbicularis : 
it was now the muscle of the healthy side which 
was affected by the galvanism, the eyelid of 
that side being closed, whilst that of the para- 
lytic side gaped as before. I next compared 
the effect of galvanism in two cases of complete 
paralysis of the arm, one hemiplegic, the other 
the result of dislocation of the shoulder. The 
muscles of the former were more, those of the 
latter less, irritable than those of the healthy 
arm respectively, as were also those of the arm 
of a patient affected with the paralysis induced 
by lead. Lastly, I compared the cases of pa- 
ralysis of the lower extremities, one arising 
after pertussis, and therefore cerebral, the other, 
I think, from disease within the lumbar verte- 
bre: in the former there was augmented, in 
the latter, diminished irritability. 
By means of these experiments and observa- 
tions we are enabled, I believe, to explain all 
the apparent discrepancies between the state- 
ments of former authors, and between each of 
them and my own. 
The observations of Nysten and others deter- 
mined that the irritability of the muscular fibre 
still existed in ordinary hemiplegia; but they 
did not extend far enongh to determine the 
comparative degree of irritability of the para- 
lytic and of the healthy limbs, or the question 
whether, in the former, the irritability was dimi- 
. nished—the event probably expected—or aug- 
mented, a result, I believe, never anticipated. 
Prochaska and Nysten and Legallois failed 
in their experiments, too, by not allowing time 
for the change in the condition of the irritability 
of the muscular fibre to take place. 
Professor Miller and Dr. Sticker, on the 
other hand, did not distinguish between para- 
lysis arising from separation from the cerebrum 
merely, and paralysis arising from separation 
from the spinal marrow, a distinction of the 
utmost importance in every point of view, and 
that which explains the phenomenon under 
discussion. The term paralysis has been used 
by all the authors whom I have quoted in too 
general a sense. This is so true that I may 
affirm that in one kind of paralysis, that which 
removes the influence of the cerebrum, and 
which is therefore paralysis of spontaneous or 
voluntary motion, there is augmented irrita- 
bility; whereas in the other, that which severs 
the influence of the spinal marrow, the irrita- 
bility is diminished or even annibilated. 
We may conclude that in cerebral paralysis 
the irritability of the muscular fibre becomes 
augmented from want of the application of the 
stimulus of volition; in paralysis arising from 
disease of the spinal marrow and its nerves this 
