IRRITABILITY. 



39 



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. 



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. 



1st. 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, 

 remained 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 



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. I 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 lovv'er extremities, one arising 

 after pertussis, and therefore cerebral, the other, 

 I think, from disease within the lumbar verte- 

 brae : 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 enough 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 Miiller 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 annihilated. 



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 



