Royal Society, 469 



by the muscular fibre to its own nervous filaments, or rather to the 

 nervous force existing in those filaments. 



Referring then to an experiment related in a preceding paper, in 

 which the lower limbs of a frog, united to the spine only by the 

 lumbar nerves, are placed astride two glasses containing water, with 

 each foot immersed, and in which a current, after traversing the two 

 limbs, and consequently the two nerves, in opposite directions, so 

 modifies at length the excitability of the nerves, that, on opening the 

 circuit, only the limb in which the current has been passing inversely 

 contracts, he shows that if in this state what may be called the ' in- 

 verse' nerve be touched by a piece of muscle, although the circuit is 

 continued, yet the limb contracts as though the circuit had been 

 broken. In fact, the muscle, by its greater conductibility, becomes 

 traversed by the current in place of the nerve. Again, if after the 

 former part of the experiment has been performed, the portions of 

 nerve which had hitherto been buried among the crural muscles be 

 dissected out, it is easily seen that their excitability has not been af- 

 fected like that of the lumbar nerves, because the current in place 

 of traversing them has traversed only the crural muscles. The nerve 

 has had its excitability modified in only that part of its course in 

 which, being laid bare and isolated, it has necessarily conducted the 

 current. 



M.DuBois Reymond( Co/wpfes i?ewcfM«)has related an experiment 

 seeming to lead to the inference that section of the spinal marrow 

 increases the excitability of the lumbar nerves, at least during a 

 certain period of time. In order to test the accuracy of this con- 

 clusion on so important a point, M. Matteucci institutes a number 

 of very accurate experiments, in which he measures the excitability 

 of the lumbar nerves after section of the spinal marrow, by means 

 of the apparatus of Breguet, used and described by him in a former 

 paper. His first results show that " the contraction excited in the 

 muscles of a frog, of which the spinal marrow has been divided from 

 twelve to eighteen hours, is stronger than that obtained under the 

 same circumstances from the muscles of a frog just killed, without 

 having been previously subjected to any injury to its nervous system." 

 But subsequent experiments have satisfied him that this result de- 

 pends not on the separation from the spinal marrow, but rather on 

 the repose in which the muscle has been permitted to remain ; for 

 without division of the marrow, nearly the same force of contraction 

 existed after the same interval of time. He finds indeed that the 

 only alteration which the excitability of a nerve undergoes by sepa- 

 ration from the nervous centres, consists in its being more readily 

 exhausted under the action of stimulants, the longer the period that 

 has elapsed since its detachment. 



The author then proceeds to relate the nature of the strict analogy 

 existing between electricity and nervous force. As electricity is de- 

 veloped under the influence of the nervous current in the organs of 

 electrical fishes, so, as a converse of this phenomenon, electricity 

 may develope the nervous force. After adverting to the well-known 

 analogy subsisting in every particular between the phenomena of 

 the electrical organ and those of muscles, he adverts to the old ex- 

 periment of passing a current through the muscles of the thighs of 



