MEDICAL BATTERIES. 



51 



The large batteries with extensive surface, which are at pre- 

 sent chiefly used in medicine, are the modified Daniell, the proto- 



Fig. 11. — Buusen's battery. 



sulphate of mercury battery of Marie-Davy, the sulphate of lead 

 battery of Marie-Davy, and the battery of Siemens (Remak's). 

 These forms will require more particular description. 



(d). The halloon hatterij of Daniell, by Parelle (fig, 12). I used 

 for a long period, for the application of continuous currents, one 

 of the modified Daniell's batteries, which, of 

 the forms then known, was that which furnished 

 the most enduring and most steady, current. 

 Instead of having the positive pole within, and 

 the negative pole without, as in the original 

 form, the poles of this apparatus had tke con- 

 trary arrangement. The zinc ]3lates, 14 centi- 

 metres in height, were amalgamated, and im- 

 mersed in a solution of sea-salt, placed between 

 the porous cell and the external vessel. The 

 porous cells containing the solution of sulphate 

 of copper were surmounted by glass balloons 

 (inverted flasks) full of crystals of sulphate of copper, moistened 

 \\ith water. This arrangement gave way to the use of a very 

 large porous cell, in the middle of whicli was a grating supporting 



Fig. 12. — A Iiauiell's ceil 

 \\ ilh Parelle's balloon." 



•^ I, tube introduced into the balloon, immersed in the solution of sulphate of 



A. C, lateral openings in the tube. D, D, copper. O, porous cell containing the 



cover of wood, pierced by two openings solution. — conductor fixed to the zinc 



for the conductors, -f rod of copper that surrounds the poroua^ell. 



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