CHAP. IX. MUSOULAE AND KEBVOUS TISSUE. 91 



we are necessarily brought to the examination of the 

 various experiments that have been undertaken from 

 the period of Galvani's celebrated discovery up to 

 the present time, in which muscular contraction has 

 been induced by means of the agency of electricity 

 upon the nerves. On the present occasion, however, 

 as it is by means of the galvanometer rather than by 

 mvscular contraction alone that the evidence proper 

 for the solution of our question might be obtained, 

 it will not be necessary to enter into a critical review 

 of the various results made known to us by our 

 predecessors; but I shall state those facts in the 

 form of a few propositions which appear to have 

 been well-established by the labours of Volta, 

 Marianini, Nobili, Matteucci, Mabshall Hall, 

 Du Bois Ketmond, and others S and to which I shall 

 have occasion to allude in the course of the inquiry. 



1st, When an electric current traverses a nerve, it 

 is only at the opening and closing of the circuit that 

 muscular contraction ensues. 



^dly. No muscular contraction occurs during the 

 passage of the current. 



^dly. After the inverse current has passed for some 

 time along a nerve, upon opening the circuit, tetanic 

 contractions are produced ; with the direct current no 

 tetanic contractions take place. 



' In Beoqueeel's Traite de rElectrieite, will be found an 

 account of the views of the earlier inquirers, and also some 

 very valuable observations of his own in regard to animal 

 electricity. I may also refer to De la Eive's Treatise on 

 Electricity, translated by Walker. 



