IRRITABILITY. 



37 



quelques jours, 1'un a la premiere attaque et 

 1'autre a la seconde, le galvanisme a determine 

 des contractions aussi fortes dans les muscles 

 du cote sain que dans cetix du cote paralyse : 

 les iris des deux cotes sont e'galement coritrac- 

 tees." " Cette propriete n'a etc 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, 1'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 

 a dctruire la moelle lombaire dans un lapin 

 age de moins de dix jours ; il faut le choisir de 

 cet age, pour que la circulation ne 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, 1'irritabilite s'y conserve, et Ton 

 peut, pendant fort long-temps, faire contracter 

 les cuisses, en irritant les nerfs sciatiques. II 

 paraitdonc qu'il se fait dans toute 1'etendue des 

 nerfs une secretion d'un principe particu- 

 lier." f 



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. 



Some interesting experiments on this point 

 have been recently performed by Professor 

 Muller and Dr. Sticker. The former cele- 

 brated physiologist observes,! " It was known 

 that, after the division of a nerve, the portion 

 cut off from communication with the brain 

 retains, for a certain time, its excitability; but 

 the question, how far the continuance of the 

 connection with the brain and spinal marrow is 

 necessary for the longer preservation of the irri- 

 tability of the nerves, and whether the muscles 

 retain their irritability when their nerves no 

 longer communicate with the central parts of 

 the nervous system, could not hitherto be an- 

 swered with certainty, and had indeed been 

 seldom mooted. Nysten had asserted that the 

 muscles of patients who died a short time after 

 an apoplectic seizure preserved their irratibility, 

 and contracted under the influence of the gal- 

 vanic stimulus, although the functions of the 

 brain had been paralyzed. 



" I had good reasons, however, for believing 



* Rechprches Physiologiques, 1811, p. 369; com- 

 pare p. 377 and 419; and Cuvier, Histoire des 

 Sciences Naturelles, tome i. p. 213. 



t (Euvres de Legallois, ed. 1824, p. 23 and 24. 



J See the excellent translation of the " Handbuch 

 der Physiologic," by William 15aly, M.D., vol. i., 

 p. 631633; and compare p. 663, 724, 727, 898, 

 &c. and Grainger on the Spinal Cord, p. 96, 97. 



that, in such cases, the nerves retain their power 

 only for a short time, losing it entirely after a 

 longer interval ; for, in experiments on the re- 

 production of the nervous tissue in a rabbit, I 

 had once observed, that the lower portion of 

 the nervus ischiadicus, which I had divided 

 some months previously, had lost all its exci- 

 tability; and a similar fact had been before ob- 

 served by Fowler. I have since performed, in 

 conjunction with Dr. Sticker, new experiments, 

 which have completely confirmed that suppo- 

 sition. To prevent the regeneration of the 

 nerves, and to withdraw more effectually the 

 lower portion from the influence of the brain 

 and spinal cord, a portion of the nerve (the 

 ischiadic) was entirely removed. The experi- 

 ments were made only on two rabbits and a 

 dog; yet the results were so constant, that they 

 are quite worthy of dependence. 



" Eleven weeks after the division of the 

 nerve in the first rabbit, it was laid bare in its 

 course between the biceps and semitendinosus 

 muscles. Contrary to expectation, and to our 

 mortification, the continuity of the nerve was 

 found to be restored. It was divided anew 

 below the cicatrix ; and it is remarkable that, 

 although the animal uttered a loud cry, the 

 section excited no contraction of the muscles. 

 The lower portion of the nerve was now ex- 

 posed to the galvanic stimulus of a single pair 

 of plates, was cut and pulled in every possible 

 way, but not the slightest muscular contraction 

 was excited. 



" For the sake of comparison, the nerve of 

 the opposite side was divided, when the animal 

 showed signs of suffering the most severe pain, 

 and violent muscular spasms took place ; and, 

 after the division, very slight irritation of the 

 nerve itself, that is to say, of the lower portion 

 of it, or merely of the muscles, excited strong 

 twitchings, even after death. 



" Ten weeks after the division of the nerve 

 in the dog, the ends were found to be reunited. 

 The experiment was performed exactly as in the 

 rabbit, and the result, as to the effect on the 

 nerve, was entirely similar : it had lost al! its 

 excitability; but the muscles still contracted 

 slightly when stimuli were applied directly to 

 them immediately after death : however, this 

 remaining irritability was gone, while, in the 

 muscles of the opposite leg, the strongest con- 

 tractions could be excited. 



" Five weeks after the nerve had been di- 

 vided in the second rabbit, we proceeded to 

 examine its state, and were the more interested 

 on account of the short time that had elapsed 

 since its division. The ends were not united ; 

 they were somewhat swollen, and connected 

 with the surrounding cellular tissue. In the 

 other instances, the portion of nerve removed 

 measured about four lines only; here its length 

 was eight lines. No contraction of the muscles 

 could be excited by irritating the nerve either 

 mechanically or by a chemical stimulus, caustic 

 potash, or by galvanism ; nor by irritating the 

 muscle itself, although the rabbit had plenty of 

 vital power. On the left side the muscles were 

 found irritable, as in the other cases, both before 

 and after death. 



