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Wm. Charles Henry, M.D., Physician to the Manchester Royal 

 Infirmary. Communicated by Wm. Henry, M.D., F.R.S. 



It has long been a subject of controversy among physiologists 

 whether muscular contraction is the immediate consequence of the 

 action of a stimulus on the muscular fibre, or whether it is neces- 

 sarily dependent on a change taking place in the nerve distributed 

 to the muscle, and excited by the stimulus. This question, the 

 author observes, is one which, from its very nature, is incapable of 

 a direct solution, because the intimate connection of nervous fibres 

 with every part of the muscles renders it impossible to distinguish 

 on which of these classes of textures the impression of the stimulus 

 is primarily made. The continuance of the motions of the heart 

 after the destruction of the brain and spinal cord, and even after the 

 entire removal of the heart from the body, has been adduced as 

 an argument of the independence of the contractile property of the 

 muscular fibre : but this argument the author considers as incon- 

 clusive, because the nervous fibres remaining in the heart, and 

 expanded on the interior of its cavities, may still be capable of per- 

 forming their usual functions, and act as the medium of excitation 

 to the muscular fibres: an hypothesis strongly supported by the 

 analogy of the voluntary muscles, which, though usually excited to 

 action by changes taking place in the central portions of the ner- 

 vous system, may yet, when removed from this influence, be made 

 to contract by irritations applied to the trunks of the nerves that 

 supply them. 



As narcotic poisons act exclusively upon the nervous system, the 

 author conceived that they might afford the means of eliminating 

 the action of the nerves, and thus enable us to discover what share 

 they contribute towards muscular contraction. On applying the 

 empyreumatic oil of tobacco, or the hydrocyanic acid, to the sciatic 

 nerves of a rabbit, he found that the functions of that part of the 

 nerve which was in contact with the poison was destroyed, and that 

 irritations applied to that part no longer excited contractions in the 

 muscles. But when the portion which had been so affected was 

 cut off, and the galvanic wire applied to that extremity of the nerves 

 which remained attached to the muscle, contractions were produced. 

 Similar results were obtained when the poison was applied directly 

 to the brain. When, on the other hand, the poison was applied 

 to mucous surfaces so as rapidly to extinguish life, the muscles 

 throughout the whole body were paralysed and lost all capability of 

 being excited to contraction. 



The inefficacy of opium applied to the cardiac nerves in arresting 

 the motions of the heart has often been alleged as a proof that those 

 motions are independent of the nerves. But the author found on 

 trial that a solution of opium injected into the cavities of the heart, 

 or introduced into the intestine, immediately arrested the muscular 

 actions of these organs. 



These phenomena appear to the author to accord best with the 

 hypothesis that the immediate antecedent of the contractions of the 

 muscular fibre is a change in the ultimate nervous filament distri- 

 buted to that fibre. 



