JIEDICAL BATTERIES. 



57 



is so arranged in the completed apparatus, that it can be moved vertically up 

 and down ; and can be fixed at any point. By this arrangement, the acid can 

 be brought into contact with the whole, or with part of the zinc and carbon ; 

 or, by shutting down the glass, can be excluded from them altogether. In 



Fig. 15.— Stolirer's battery. 



I ig. lb — jMunhead's battt-rv. 



the latter case, the acid will only fill the lower third of the glass. The 

 advantages arising from being able to remove the elements at once and 

 Avithout difficulty from the exciting fluid, and from the equal facility with 

 which they may be brought into action, are obvious. If the battery be in 

 daily use, the zinc would require to be re-amalgamated, and the acids renewed 

 every six or eight weeks. Twenty-four or more pairs of the elements are 

 arranged upon a stand to form a battery for medical use. 



Muirlteads Battery. — This form of battery, as adapted for medical puri^oses 

 by Mr. Becker, of the firm of Messrs. Elliott Brothers, is in use at the National 

 Hospital for the Paralysed and Epileptic. It is a modification of Daniell's 

 battery, and has been largely employed in this country for the electric telegrai)h. 

 The tension of the battery is low, but the action is very uniform. Tlie ele- 

 ments consist of a zinc plate (fig. 16, z), unamalgamated (3| x If x |- inches), 

 and of a thin copper plate, 3|x3| inches (fig. 16, c). The copper plate 

 is immersed in a solution of sulphate of copper, placed in a porous cell 

 (fig. 16, p) ; tiie zinc plate i^. immersed in simple water, contained, with the 

 porous cell and its content?.', in a quadrangular porcelain vessel. The j^orce- 

 lain vessels are constructed in couples, each holding two pairs of elements, 

 and five of these couples are packed in a strong oak box. The arrange- 

 ment of the battery adopted at the National Hospital for the Paralysed and 

 Epileptic, as least complex, is that shown in fig. 17, in which ten boxes, con- 

 taining 100 pairs of elements, are placed upon a simple open stand. 



In using this battery for medical jnirposes, single jmirs of elements are not 

 brought into action. The pairs, to the eightieth pair, are grouiDed in sets of 

 five ; and the remaining twenty are grouped in tens. The terminal wires 

 of the cells thus arranged, are attached to buttons in rear of two re- 

 volving discs, numbered respectively from 5 to 45, and. from 50 to 100; 

 ■and by turning the discs, the operator, without detaching the conducting 

 wares with which the rheoi^hores are connected with the instrument, can 

 bring into play the current from as many sets of cells as he desires. 



When in daily use, the cells require to be recharged, and the zinc plates 

 cleaned every two months ; and new zinc plates are needed every eighteen 



