CHAP. XT.] MATTEUCCI'S PHYSIOLOGICAL RESEARCHES. 385 



direct current, or from opening the inverse ; and that a sensation is caused 

 by the direct current on opening, but by the inverse on closing. 



Matteucci repeated these observations on the sciatic nerves of the rabbit, 

 devoting one nerve to the direct, the other to the inverse, current. On closing 

 the direct current, contractions were produced in the muscles of the limbs and 

 back, with marked signs of pain ; the same phenomena result from closing 

 the inverse current, and from opening both. The signs of pain were greatest 

 at the closure of the inverse current, and the contractions were most at the 

 closure of the direct current. The commencement and the interruption of an 

 electric current of a certain intensity, acting upon a certain portion of the 

 nervous system, are followed by the same phenomena, whatever be the direc- 

 tion of this current in the nerve. After some time, which is shorter as the 

 current is more intense, the phenomena take place in a different manner. 

 Upon interrupting the direct current, the contractions of the muscles of the 

 limbs are feeble, but there are signs of pain, and the muscles of the back are 

 contracted ; but, when the direct current is closed, the effects are limited to 

 contractions of the posterior limbs. When the inverse current is used, con- 

 tractions of the muscles of the back and signs of pain occur on closing it, 

 while the contractions of the limbs are slight ; but, on the interruption of it, 

 contractions of the limbs alone take place. 



The following tabular view will exhibit these latter results more clearly. 



C contractions in muscles of posterior 



( closm S- ' limbs. 

 Direct current ../ i j c j j. 



\ t marked signs or pain, and contraction 



^ opening . . < of muscles of the back. 



I feeble contractions of posterior limbs. 



f signs of pain, contractions of muscles 

 f closing . . < of back, and feeble ones of the pos- 

 Inverse current . . < ( terior limbs. 



( opening . . contractions of the posterior limbs. 



So that, after the lapse of a little time, the phenomena produced by closing 

 the inverse current, becomes precisely the same as those on opening the 

 direct, and vice versil. 



The contractions of the muscles of the back, which are supplied from 

 nerves which come off above the point of excitation, are due to the irritation 

 of the nervous centre, affected through sensitive nerves ; for these contrac- 

 tions cannot be produced if the portion of the cord from which the nerves 

 arise have been removed. 



After the nerve has been exhausted, so as to yield the phenomena of the 

 second period, as shewn in the table, it may be excited to act as at first, 

 either by increasing the intensity of the current, or by exciting points of the 

 nerve nearer its peripheral extremities. 



A simple experiment illustrates the different effects of the direct and inverse 

 current in a very striking manner. The limbs of a frog are prepared accord- 

 ing to the ordinary method of Galvani. If a current be passed from one side 

 to the other through the lumbar nerves, it is plain that it will be direct in the 

 nerves of one side, and inverse in those of the other side. During the first 

 period, there are contractions both on completing and interrupting the 



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