HOMOGENEOUS DIVERTING VESSELS. 165 



there are combinations of metals with fluids which are 

 free from these faults. Two pieces of zinc, the surfaces 

 of which have been amalgamated by smearing with 

 quicksilver — which have, therefore, been equally covered 

 with a coating of zinc-amalgam, a combination of zinc 

 and quicksilver — act as though entirely homogeneous if 

 they are immersed in a solution of sulphate of zinc; and 

 these metals retain their homogeneity even when elec- 

 tric currents traverse the metals and the fluids. The 

 wire of the multiplier may be connected with strips of 

 amalofamated zinc of this sort, and these mav be im- 

 mersed in a solution of sulphate of zinc without any 

 deflection being indicated even by a very sensitive mul- 

 tiplier. While, therefore, it might lead to serious error 

 if the wires of the multiplier were brought into imme- 

 diate contact with the animal substances to be ex- 

 amined — as electricity would, in such case, be generated 

 at the point of contact itself — it is possible, by using 

 this amalgamated zinc and solution of sulphate of zinc, 

 to exclude any foreign source of electricity, and, pro- 

 vided that the animal tissue is properly inserted, to 

 be sure that the observed deflections of the magnetic 

 needle are really due to electric forces situated in the 

 animal substances themselves. The point to be aimed 

 at in this experiment is, therefore, to place the animal 

 substances in such a position that any currents gene- 

 rated in them can only pass to the wire of the multi- 

 plier through the zinc solution and the plates of amal- 

 gamated zinc. 



6. In order to attain this object, du Bois-Reymond, 

 to whom is chiefly due our knowledge of the electric 

 phenomena of animal tissues, arranged the apparatus 

 in the following way (fig. 39). The ends of the wires 



