218 LOCALIZED ELECTEIZATION. 



sixteen millimetres of section. In the centre of each carbon was a cylinder 

 of zinc of the same height, a centimetre and a half in diameter. This 

 battery gave too great a quantity of electricity, in direct proportion to its 

 extent of surface. 



Its electrolytic action was such that, with forty-two elements immersed 

 scarcely a centimetre, its rheophores produced vesication of the skin in two 

 or three minutes. I therefore requested M. Euhmkorff to diminish the 

 surface by two-thirds, and he has done so by constructing the zinc and 

 carbon as shown in the figure. They measure nine centimetres by eight 

 millimetres, and act only by the surfaces that are mutually opposed. I have 

 also rei)laced the solution of bisulj^hate of mercury by a weak solution of the 

 protosulphate. 



As thus modified, the battery may be used for all electro-physiological or 

 therapeutic aiDplications of continuous ciirrents. It has also been rendered 

 less heavy and less costly by diminishing the bulk of the carbons. The 

 gi'eater or less degree of immersion of the elements in the solution is obtained, 

 as I have said, by raising or lowering the double platform C. To raise this 

 platform, with the elements that are fixed to it, it may be lifted more or less 

 by the handle, m, and its descent is prevented by the catch, d", which falls 

 between the teeth of the pinion, and which must be lifted in order to lower 

 the platform. The teeth of the pinion are so arranged that each one 

 allows the j^latform to descend a single millimetre. 



The mechanism of the system of gradual immersion or emergence of the 

 elements is assuredly simple and good, but it leaves something to be required 

 with regard to the exact graduation of the electrolytic action of the battery. 

 The indicator does not show precisely the degree of immersion of the elements, 

 except on the condition that the liquid in the cells should stand always at 

 the same level. But, as the cells are not closed, the height of the liquid is 

 constantly diminished by evaporation. I have therefore had a line marked 

 on the walls of the cells, to show the height at which the liqiiid should be 

 kept, and a large ojicniug made in the side or front of the box, and filled with 

 glass, through which the height of the liquid may be seen. 



2. The battery is divided into six rows, each composed of seven elements. 

 The screws of the first row, which fix the zinc and carbon to the plat- 

 form C, are furnished with openings in which to place the conductors; so 

 that the current may be increased or diminished by from one to seven elements. 



This graduation is particularly aj^plicable to delicate physiological experi- 

 ments. The metallic stem y' (graduator of the tension), which M. Euhmkorff 

 has added to the'apparatus at my desire, is so constructed as to graduate the 

 tension of the currents, without producing intermissions. When it is pushed 

 in the tension of the battery is at its maximum, and as it is withdrawn the 

 number of elements is diminished by sevens, as shown by the divisions 

 marked upon the stem, without its being necessary to change the conductors 

 fixed to the knobs n and ^5. 



When the battery is exhausted, the platform C is entirely removed fi'om the 

 box by the handle vi, and the cells are refilled with fresh solution. For that 

 purpose, water is poured into them to the level of the horizontal line already 

 mentioned, and a single gramme of protosulphate of mercm-y is added to each, 

 by means of a little measure which is attached to the apparatus. This mani- 

 pulation is easy, and can always be exactly done by the means indicated above. 



One of the principal advantages of this battery is the facility of gra- 

 duating the degree of immersion of the elements ; or, in other words, of 

 measviring ihe electrolytic action while preserving the force of the tension. 

 The possibility of obtaining from it a weaker or more powerful electrolytic 

 action has the great advantage of rendering it equallj' apjilicable to cases for 

 which the use of the continuous ciirreut by reflex action is required, and to 

 those in which the surgeon wishes for electrolytic effects. 



In M. Euhmkoiff's chloride of silver battery the carbons are replaced by 

 cylindrical stems of chloride of silver. 



