591 FUNCTIONS OF THE CEREBRO -SPINAL NERVOUS SYSTEM. 



string, moistened with water or saliva, bo made to take the place of the nerve, the 

 needle moves, as it moves under the action of electrotonus, when the nerve is acted 

 upon, as it moves under the action of anelectrotonus it' the anode be next the gal- 

 vanometer, as it moves under the action of cathelectrotonus if the cathode be in this 

 position. And so also if cotton thread, or silk thread, or a thread-like strip of 

 gutta-percha, similarly moistened with water or saliva, be substituted for the piece 

 of common hempen string, the movements of the needle belonging to electrotonus 

 beinc always produced if only the vo'.taic conditions for producing them are pro- 

 vided. 



Here, too, is the place to mention another fact, which is really complementary to 

 the facts which have been mentioned ; namely, this, that electrotonic movements of 

 the needle are not met with when the experiments for producing them are repeated 

 upon a piece of metal wire; for unless this fact be taken in connection with the 

 others, it is very difficult to say why these movements should be present in some cases 

 and absent in others. 



Shortly before these facts were brought to light by the independent inquiries of 

 .Dr. Radcliffe, Matteucci had also discovered First, That electrotonic movements of 

 the needle are to be obtained, not only from living nerve, but also from dead nerve, 

 as well as from narrow strips taken from the substance of brain or bladder ; and, 

 secondly, that such movements are not to be obtained if the body experimented on 

 be a wire of amalgamated zinc, covered with cotton or linen thread, and soaked in a 

 saturated solution of sulphate of zinc ; and thus, with this strong additional evidence 

 in their favor, the facts under consideration cannot well be called in question. 



It is very plain, then, that the electrotonic movements of the needle are not to be 

 referred to modification of the nerve-current produced by the voltaic current, but it 

 is not easy to get beyond this negative conclusion. Matteucci refers them to polar- 

 ization, their absence in the case of the amalgamated zinc wire, coated with thread 

 soaked in saturated solution of sulphate of //me, arising, as he believes, from the fact 

 that such wire is unpolarizable ; but this view does not account for the absence of 

 these movements, when the wire employed in the experiment is made of copper, or 

 silver, or platinum, without anything being done to it to prevent polarization. Dr. 

 Eadcliffe has another way of accounting for the presence or absence of the move- 

 ments in question : for the presence, by supposing that the free electricity which is 

 liberated at the voltaic poles when nerve or other bad conductor is placed between 

 them, may so overflow towards the galvanometer, and into the coil, as to act upon 

 the needle and make it move, as it moves in anelectrotonus, if this free electricity be 

 positive, as in cathelectrotonus. if negative ; and for its absence when a good con- 

 ductor like wire is planed between the poles, by supposing that in this case tin-re is no 

 overflow of free electricity from either of the poles towards the galvanometer and 

 into the coil, for tin- simple reason, that the presence of the good conductor between 

 the poles prevents the liberation of free electricity at the poles; and in justification 

 of this view, he points to the fact that similar movements of the needle may be actu- 

 ally brought about by passing free electricity through the coil, and that this free 

 electricity is actually present when electrotonic movements are present, and absent 

 in the contrary cases. 



Movements of the needle strictly corresponding with the electrotonic movements 

 may be caused by the electricity set free by means of a fractional machine, if this 

 electricity be made, to pass through the coil of the galvanometer in the way in which 

 it is supposed to pass in electrotonus, the movement agreeing with that of anelectro- 

 tonus when the electricity is positive, and with that of cathelectrotonus when it is 

 negative; and thus there' is no intrinsic improbability in the notion that the electro- 

 tonic movements of the needle may be brought about by the action of free electricity. 

 There is also very conclusive evidence to show that the two electrotonic regions 

 are actually charged as they arc supposed to bo charged in the case where the elec- 

 trotonic movements of the needle are present, the anelectrotonic positively, and the 

 cathelectrotonic negatively, and that these charges are absent when the movements 

 are absent. Thus, if a long piece of nerve be stretched out upon a plate of paraffin, 

 with its mid. He portion lying across the poles of a voltaic battery, the state on closing 

 the circuit, as made known 'by touching the nerve here and there with the electrode 

 belonging to the insulated pair of quadrants of the new quadrant electrometer, i- found 

 to be that which is shown in the accompanying figure ( Fig. 205), the anelectrotonic 

 region, which is left unshaded, being charged positively as is indicated by the dotted 

 line with the -(- signs over it; the cathelectrotonic region, which is shaded, being 

 charged negatively, as is indicated by the clotted line with the signs over it as a 

 stale of charge, the degree of which is equal to that of the pole outside the pole, but 

 not so inside the pole ; for inside the pole it falls regularly from the pole, where it is 



