114 NERVOUS SYSTEM. 



intensity of the muscular current. 1 The existence of the 

 nerve-current has, as far as we know, no more physiological 

 significance than the analogous fact observed in the muscular 

 tissue. It is presented in nerves removed from the body, and 

 has no relation to their functional activity, whether in nor- 

 mal action or excited by artificial stimulation. 



Effects of a Constant Galvanic Current upon the Nervous 

 Irritability. Aside from the disorganizing effect upon the 

 nerves of a powerful constant current, which is due solely 

 to decomposition of their substance, a feeble current has been 

 found to exert an important influence upon the nervous 

 irritability, according to the direction in which the current 

 is passed. The law in accordance with which this influence 

 is exerted .is stated by Matteucci as follows : 



" A continued electric current passed through a mixed 

 nerve, the crural or the lumbar, for example, modifies the 

 excitability of the nerve in a very different manner, accord- 

 ing to its direction. The excitability is enfeebled by the 

 passage of the direct current, and, on the contrary, it is pre- 

 served and augmented, at least within certain limits, by the 

 inverse current. The time necessary in order that the cur- 

 rent shall produce this modification is proportionate to the 

 degree of excitability of the nerve and in inverse ratio to the 

 intensity of the current. After the breaking of the circuit, 

 the modification of the nerve tends to cease at a period that 

 is short in proportion as the excitability of the nerve is great 

 and the intensity of the current is feeble. This proposition 

 explains the difference in the electro-physiological effects of 

 the continued current according to its direction, the well- 

 known phenomenon of voltaic alternations, and the pe- 

 riods discovered and specially studied by Marianini and 

 JSTobili." 3 



This law has been carefully studied and formularized, as 

 above, by Matteucci, but its discovery is attributed by physi- 



1 MATTEUCCI, Cours tfehctro-physiologie, Paris, 1858, p. 122. 2 Ibid., p. 30 



