Dr. Radcliffe on the Action of a Galvanic Current upon Nerve. 399 



tinuous and induced currents are made to act upon the nerve. Thus 

 the induced currents produce contraction if applied after the direct 

 continuous current, but not if applied after the inverse continuous 

 current. Nay, it would even seem as if the direct current is actu- 

 ally favourable to contraction ; for a solution of salt, which of itself 

 is too weak to produce tetanus when applied to a nerve, will have 

 this effect when a direct current is made to pass through another 

 portion of the same nerve. In performing this experiment, Professor 

 Eckardt proceeds as follows : — First of all he tetanizes a frog's 

 hinder limb by placing a portion of the nerve nearest to it in a strong 

 solution of salt ; after this he adds water until the strength of the 

 saline solution is no longer sufficient to keep up a state of contraction 

 in the muscles ; then, all things being as they were, he passes the 

 direct current through a portion of nerve which is not immersed in 

 the solution. The result is that the tetanus immediately returns. 



Now, on comparing this last fact with the two previous facts, we 

 may have, as it seems to the author, some insight into the mode in 

 which the galvanic current acts upon nerve in the period of alternate 

 contraction. On the one hand, it is seen that tetanus is prevented or 

 arrested by the inverse current ; that is to say, tetanus is prevented 

 or arrested when (as the first and second facts show) the galvanic 

 current coincides in direction with, and imparts power to, the nerve- 

 current. On the other hand, it is seen that tetanus is not prevented 

 or arrested by the direct current ; that is to say, tetanus is not pre- 

 vented or arrested when (as the first and second facts still show) the 

 galvanic current differs in direction from, and diminishes the power 

 of, the nerve-current. The one result is in harmony with the other ; 

 for if contraction is counteracted by imparting power to the nerve- 

 current, it is to be expected that contraction will be favoured by 

 detracting power from the nerve-current ; and certainly it is no 

 matter of wonder that contraction should be favoured by detract- 

 ing power from the nerve- current, for it is an established fact that 

 rigor mortis is coincident with absolute extinction of the nerve and 

 muscular currents, and that ordinary contraction is attended by un- 

 mistakeable weakening of these currents. It is also an established 

 fact, that muscular contraction is produced by the discharge of ordi- 

 nary statical electricity, and not by the charging and charge. Nay, it 

 is not improbable that the contractions at the beginning and ending 

 of the current, in the period of double contraction, which contractions 

 have been referred by the author to the action of induced currents, 

 may in reality be due to the withdrawal rather than to the commu- 

 nication of these currents ; for these induced currents are of moment- 

 ary duration, disappearing at the very instant of appearing, and 

 exhibiting peculiarities in disappearing which connect the disappear- 

 ance with the discharge of statical electricity, rather than with the 

 more quiet cessation of current electricity. 



A.nd if this be so — if the inverse current antagonizes and the 

 direct current favours contraction — then we may in some degree un- 

 derstand how it is that contraction occurs alternately at the beginning 

 of the direct, and at the end of the inverse current. 



