It is possible to reduce some of the reptile tribes to a state approaching that of animals still lower in the scale, by removing, by very slow degrees, successive portions of the ner vous masses. This is most readily done in animals in which the respiration is already low, and the irritability high, as in the fwtus, in the very young animal, in the reptile, &c., as in the experiments of Legallois,' M. Serres,t myself,1 &c.
There is, even in animals most tenacious of life, one kind of mutilation—one kind of in jury not well borne. As the blood is in its lowest condition of stimulus, it cannot be withdrawn with impunity ; even frogs soon perish if their blood be allowed to flow. As the irritability, on the other hand, is high, certain stimuli, as galvanism, slightly elevated tem peratures, &c. are speedily fatal. The batra chia are promptly destroyed by immersion in water of a temperature of 108° of Fahr., and some fish and crustacea perish in great num bers under the influence of a thunder-storm. It is a singular fact, that the fish alone, whose food is found amongst animals of a high irrita bility, should possess an electrical organ for the destruction of its prey.
The application of stimulus has uniformly a tendency to reduce the degree of irritability. The exclusion of all stimuli allows its augmen tation. During active exercise the irritability is diminished; during sleep it is proportionally augmented.
We are nowled to take another view of this sub ject of irritability. What is its source ? Bow is it renewed when it hasbeen exhausted? These ques tions lead us to take up another of great interest, to physicians especially, viz. what is the condition of the muscular irritability in those cases in which the influence of the cerebrum, or of the spinal marrow, or both, isremoved respectively? We cannot discuss this subject more clearly than by adducing the following observations, read before the Royal Medico-Chirurgical Society and published in its Transactions, in the year 1839.
The utmost discrepancy of opinion prevails amongst physiologists and medical writers upon this subject. Prochaska, Nysten, and Legallois state, that the irritability of the muscular fibre remains in paralytic limbs ; whilst Professor Muller and Dr. Sticker assert the contrary. No attempt has been made to reconcile a contra diction not very honourable to our science. To, explain this discrepancy of opinion is one of the objects of this communication.
The authors to whom I have referred, misled by the generic term and idea of paralysis, have not sufficiently distinguished between its dif ferent species. Yet it will be found, as we pro ceed, that this distinction is of the utmost im portance in the explanation of the phenomena. In fact, cerebral paralysis, or that which re moves the influence of the brain, and spinal paralysis, or that which removes the influence of the spinal marrow, are in totally opposite conditions in reference to the irritability of thel muscular fibre in the limbs severally affected ;,1 facts equally obvious in experiments and in clinical observations. I must make quota tions of some length, for these are necessary to show the present state of the science. I shall
then proceed to the detail of my own investi gations.
The first distinct notice of this subject which I think it necessary to adduce, is contained in the following extract from the Opera Itlinora o Prochaska:* " Vis nervosa qua in nervis a commercio cum cerebro separates superest, non unit alterftve musculi contractione, quam irri tati cient, exhauritur, sed millenis plane vulsionibus excitandis par est ; quod expertus sum in rank cui medullam spinalem in dorsol abscidi. Supervixit huic vulneri aliquot die bus; interim irritando medulla spinalis partem earn, qua erat infra sectionem, convulsiones in artubus inferioribus excitavi toto tempore, quo supervixit, plane innumeras ; neque extrerui tates inferiores prius mortua sunt, quam tota rana; Dein quod vis nervosa in nervis diu persistere possit citra cerebri auxin= probare videntur musculi paralytici, in quorum nervis ob cornpressionem aliquam praternaturalem t turn commercium cum cerebro sublatum est, nihilominus tauten ii stimulo electricie scintilla longo jam tempore paralytici musculi convel luntur." More detailed remarks were made by Nysten, and these, from being founded upon very dis tinct post-mostem experiments on the human subject, have excited more attention. This ce lebrated physiologist observes, " Chez deux apoplectiques qui avaient sneer:1mM an bout de I quelques jours, l'un a la premiere attaque et I'autre a la seconde, le galvanisme a determine des contractions aussi fortes dans les muscles du cote sain que dans ceux du cote paralyse : les iris des deux cotes sont egalement contrac tees." " Cette propriete n'a ete completement aneantie dans les organes musculaires des deux sujets qu'environ 12 heures apres la mort; et on n'a observe aucune difference dans les mus cles paralyses." Legallois makes similar remarks, founded upon experiments made upon animals. He observes, " M. Nysten a montre que dans les paralysies les plus completes, l'irritabilite se conserve dans les membres paralyses tout aussi bien que dans ceux qui ne le sont pas. J'ai obtenu un resultat semblable d'un experi ence que j'ai souvent repetee. Elle consiste it detruire la moelle lombaire dans un lapin age de morns de dix jours ; it faut le choisir de cet hge, pour que la circulation tie soit pas ar retee, et qu'il puisse continuer de vivre. Quoi que dans cette experience, le train de derriere soit frappe de mort, et que ses nerfs ne puis sent plus recevoir aucune influence de la mo elle epiniere, l'irritabilite s'y conserve, et l'on peut, pendant fort long-temps, faire contracter les cuisses, en irritant les nerfs sciatiques. II parait done qu'il se fait dans toute l'etendue des nerfs une secretion d'un principe particu lier." fi From these quotations from Nysten and Le gallois we should be led to the conclusion that the muscles of paralytic limbs, in all cases of hemiplegia and of paraplegia, simply retain their irritability. From another series of ob servations, made by philosophers equally worthy of our confidence, we should be led to an op posite conclusion.