232 Natural-Philosophical Colleclions. 



on the other, when the copper plate is there, the passage is rendered difficult for 

 the resinous fluid, and facilitated for the vitreous. There is no reason, therefore, 

 for a difference of results. But in the theory of one fluid, it is easy to conceive, 

 that, in the first case, the electric fluid which is diffused, as if by radiation, 

 through the liquid, would find the passage more difficult than in the second case, 

 and consequently the electro-magnetic effect, which is known to depend princi- 

 pally upon the rapidity of the electric current, should be less in the first case than 

 in the second."* — An7i. de Chimie, xlii. 131. 



Physiological Phenomenon produced by Electricity. — Professor Marianini of 

 Venice has stated, in a memoir published some time since, that a difference ex- 

 isted in the contractions of a frog when the electricity acted immediately upon 

 the muscles, and when it acted upon the nerves which presided over the muscular 

 motions : the former were called idiopathic convulsions, and the latter sympathic 

 convulsions. The difference consists in this, that the former contractions occur 

 in whatever directions the current of electricity traverses the muscles, whilst the 

 latter takes place only when the current which traverses the nerves proceeds in the 

 direction of their ramification. 



From this it follows that, when a current traverses a limb in the direction of 

 the nerves, the two shocks should occur together ; but, when it proceeds in the 

 contrary direction, only the idiopathic convulsion should be produced. In the 

 first case, therefore, the contraction should be stronger than in the second. 



If the right hand be in contact with the positive pole of a voltaic battery, and 

 the left hand equally in contact with the negative pole, a contraction is felt in 

 both arms every time the circuit is completed, but stronger in the left arm than 

 in the right. If the direction of the current be inverted, the right arm feels a 

 more powerful convulsion than the left. 



If a hand be in contact with the positive pole, and a foot in contact with the 

 negative pole, the circuit will be in the direction of the nerves of the leg, but not 

 in the arm ; and the contraction is much stronger in the leg, where the two ef- 

 fects are simultaneous, than in the arm, where the idiopathic effect only is felt. 

 The same effect takes place if the electricity is passed from tlie shoulder to the 

 hand, from one foot to anotlier, from the knee to the foot, &c. &c. 



This striking difference varies in different persons, especially in those who are 

 paralytic. The current from eighty pairs of plates, being passed from the hand 

 to the slioulder of a person struck with hemiplegia, the muscles of the arm were 

 scarcely contracted at the same place, where the convulsion was very strong, when 

 the current was passed from the shoulder to the hand. 



Sometimes this difference existed only in one limb A woman, who had lost 



the use of the lower limbs in consequence of an inflammation of the spinal mar- 

 row, felt the left foot contract with most force when it touched the negative pole 

 of the pile ; the riglit foot contracted with equal force, whether it was in contact 

 with the positive or negative pole. This effect appeared to be due to a loss of 

 nervous sensibility in the right foot, so that they had become indifferent to the 

 direction of tlie electric current. 



If a finger be immersed as far as the second joint in water, connected with the 

 positive pole of a battery containing twenty -five or thirty pairs of plates, and the 

 circuit be completed by touching the negative pole with a metallic cylinder, held 

 in the other hand wetted, a sliock is felt in the finger, not extending beyond the 

 second joint ; if the direction of the current be reversed, the shock is felt in the 

 third joint. Upon giving attention, it will be found that the first shock is made 

 external, and accompanied by a distressing sensation ; whilst the second shock is 

 more deeply felt, and is accompanied by no particular sensation at the place where 

 the finger touches the wa'ter. The effects are accounted for by the supposition 

 tliat, when the finger touches the negative pole, the simultaneous occurrence of 



• Vide a paper on this subject by our correspondent Mr. Kemp, in the 1st 

 vol. of this Journal, p. 91. 



