180 Miscellanie.", 



proportionate lo tlie energ}" of the chemical action, A solution of 

 pure sulphate of zinc deprived of interposed air, cither by heat or 

 by the air pump, and which exerts no chemical action either on the 

 copper or zinc, produces an electric current more energetic than the 

 the solutions of all other salts with the exception of sal ammoniac- 

 What is the chemical action also in the electric current produced by 

 the thermo electric pile ? — Ann. cle Cliimie. Juillet, 



MECHANICAL PHILOSOPHY. 



1 . Shocks hy the electric currents. — Professor Marianini of Ve- 

 nice maintains that there is a difference between the contractions 

 produced by the immediate action of electricity on the muscles, (which 

 he calls idiopathic,) and those which arise from its action on the 

 nerves which preside over the motion of the muscles, (which he 

 names sympathetic.) Idiopathic contractions are produced when 

 electric current takes either direction, while the sympathic are pro- 

 duced only when the current passes in the direction of the ramifica- 

 tion of the nerves. Hence, when an electric current is passed 

 through a limb in the direction of the nerves, the two shocks are 

 simultaneous ; but, if the current proceed in the other direction the 

 idopathic contraction only is perceived. 



If the right hand touches the positive pole of a battery, and the 

 left the negative, the shock is felt more forcibly in the left arm ; but 

 if the current passes in the other direction, the right arm is more 

 affected than the left. 



If one hand communicate with the positive pole, and one foot at 

 the same time with the negative pole, the shock is much stronger in 

 the leg in which it is both idiopathic and sympathic, than in the arm, 

 where it is only idiopathic. The same difference ensues in passing 

 the shock from llie shoulder to the hand, from one foot to the other, 

 from the thigh to the foot, &c. This difference is greater in some 

 persons than in others, especially if paralytic. In a man affected 

 with hemiplegia, the shock was very strong when the current passed 

 from the shoulder to the hand, but was scarcely sensible in the other 

 direction. 



In some cases of paraplegia this difference is perceived only in one 

 member. A woman who had lost the use of her lower limb by an 

 inflammation of the spinal marrow, was shocked in her left foot more 

 strongly when in contact with the negative pole ; but the right foot 



