10 MUSCULAR IRRITABILITY. 



Are the nerves the sole conductors through the medium of which all 

 stimuli necessarily act on the muscles ? * Some singular results obtained 

 by Dr. E. Harless,f from experiments undertaken for the purpose of 

 determining the relation in which the nervous influence stands towards 

 the irritability of muscular tissue, will, if confirmed, throw doubt on 

 the truth of Miiller's opinion that the functional integrity of the 

 nerves ramifying in the muscles is necessary for the excitement 

 of muscular contractions, and that the muscles themselves are not 

 susceptible of the direct action of stimuli. Having exposed rabbits 

 to the influence of the vapour of ether, until they were so far over- 

 powered by it that no movements of their bodies could be excited by 

 means even of galvanism, they were killed by opening the carotid arteries, 

 and the brain and spinal cord exposed. On galvanizing these nervous 

 centres not the slightest movement of the body resulted, but when the 

 galvanic stimulus was applied to the muscles of the trunk, violent contrac- 

 tions at once ensued. Galvanizing the crural nerve produced not the 

 slightest action of the muscles of the corresponding leg, but these muscles 

 were thrown into immediate contraction when the stimulus was applied 

 directly to themselves. Similar results were obtained by galvanizing the 

 nerves and then the muscles of other parts of the body. The result in all 

 cases appeared to point to the conclusion that the muscular tissue pos- 

 sesses within itself an inherent power of contraction, independent of the 

 influence of the nerves distributed to it ; for, in these experiments, the 

 nervous system was so far overpowered by the ether, that no amount of 

 irritation of it could excite muscular contractions, while these contractions 

 were at once induced when the irritation was applied to the muscular 

 tissue itself. 



* Miiller's Physiology, p. 898. t Miiller's Archiv. 1847, p. 228. 



