592 FUNCTIONS OF THE CEREBRO - SPINAL NERVOUS SYSTEM. 



opening and closure ; and with strong currents, the closing contraction pre- 

 ponderates with centrifugal currents, and the opening contraction with cen- 

 tripetal. As regards the reactions of sensory nerves, it is maintained by 

 Pfliiger that the effects produced by electrical stimulation .are dependent 

 upon the force of the current, except that, as might be expected from the 

 direction in which they ordinarily conduct their impressions, a kind of in- 

 verse relation exists. 



478. Those who hold with Hermann and Ouimus, with whom Ranke is 

 to some extent in accord, that many of the electric phenomena presented 

 by nerve and muscle are dependent upon chemical action, extend this view 

 to the explanation of the different conditions of electrotonus. Ouimus, 1 for 

 example, refers to an experiment made by Matteucci, which consists in 

 covering a platinum wire a yard in length with tow. The wire is dipped in 

 salt, and arranged as in the experiment for showing electrotonics. ""On pass- 

 ing a current of electricity through a given portion of it, a strong electro- 

 tonic condition is established, even at a distance of eighteen inches or more. 

 It would hence appear that the electrotouic state is not one that is peculiar 

 to the nerves. 2 They further offer a very simple explanation of the anelec- 

 trotouic and cathelectrotonic zones of Pfliiger. They contend that the pas- 

 sage of an electric current through a nerve is attended by an electrolytic 

 action resulting in the formation of acids around the positive pole and of 

 alkali around the negative, which is sufficient to explain all the phenomena, 

 since acids lower whilst alkalies exalt the excitability of the nerve. Pflii- 

 ger, from the results of his experiments, laid down the following law: A 

 certain length of nerve being given, this is excited by the supervention of 

 cathelectrotonus and by the disappearance of auelectrotonus ; but it is not 

 excited by the disappearance of cathelectrotonus nor by the supervention of 

 auelectrotouus. This law has been slightly modified by Cyou, who formu- 

 lates it as follows : A nerve is excited when its molecules pass from their 

 ordinary state to one of greater mobility (cathelectrotonus), or when they 

 pass from a state of less mobility (auelectrotonus) to the ordinary state. 

 The nerves do not, on the contrary, experience any excitation, either when 

 they pass from their ordinary to a state of less mobility (anelectrotouus) or 

 on their passage from a state of greater mobility (cathelectrotonus) to their 

 ordinary state. 3 Onimus maintains that all these alternations of commotion 

 which have received so much attention at the hands of numerous observers 

 are explicable by remembering two well-established facts First, that the 

 descending or direct current is that which acts most energetically on motor 

 nerves, or, in other words, the descending current is that which most strongly 

 calls forth muscular contraction ; and secondly, that every current when ap- 

 plied to a nerve determines a current in the opposite direction at the mo- 

 ment of its cessation. Thus each time that a nerve is electrified with an 

 ascending current a descending current is developed at the moment of 

 breaking in the interior of the nerves, and contrariwise at the moment when 

 a descending current is broken an ascending current is formed. In accord- 

 ance with this, Onimus gives the subjoined table, obtained by electrifying 

 nerves without the direct application of the poles to the nerve, which he 

 contends interferes with the results, since it causes local electrolytic action. 

 It will be seen to resemble the scheme given by Nobili. 



1 Robin's Journal clc 1'Anatomic, 1874. 



2 Kanke, however, states explicitly that neither moist conductors, nor the muscles, 

 nor dead nerves, exhibit the phenomena of eleetrotonus. Physiologic, 18T2, p. (Jl-i. 



3 Cyon, Princeps d'Electrotherapie, 1873, p. 103. 



