MEDICAL BATTEEIES. 



53 



Fig. 13.— Ciil IVoni :Murie-D!ivy's 

 protosulphute of mercury battery .« 



as constant as that of a Daniell's pile. I have constructed in 

 my rooms a battery of proto-sulphate. of mercury, of forty ele- 

 ments, like that used at the Ministry of the 

 Interior. I have kept it in action for com- 

 parison with the Daniell's battery, and for 

 the performance of some new electro-physi- 

 ological and therapeutical experiments upon 

 the most constant cuirents. During more 

 than eight months it has been in action, 

 preserving nearly all its original power. I 

 have simply poured into it, from time to 

 time, a little water to fill up the cells. This 

 battery has not appeared to me to be so 

 sensitive to variations of temperature as 

 that of Daniell ; and, during the winter, it has not broken a single 

 porous cell. Its elements have only one-third the surface of those 

 of Daniell ; and, consequently, it occupies much less space, and 

 gives a smaller quantity of electricity. It possesses, however, a 

 greater electro-motive power than the battery of Daniell. 



Unquestionably, in some respects, the battery of sulphate of 

 mercury is inferior to Daniell's. Thus it polarises more ; and 

 wastes more rapidly nnder the influence of closure of the current 

 by a metallic conductor, especially when the current is too long 

 closed. My electric clock, for example, Avhich closes the circuit 

 for one-half of each second, exhausts in a few days (in three days) 

 a sulphate of mercury battery, the porous cell of which has been 

 filled by the salt ; although it will go for three weeks with a 

 Daniell's battery, preserving a sufficient force. 



Fortunately, however, this polarisation and rapid exhaustion of 

 the sulphate of mercury pile, under the influence of too prolonged 

 a current, are not observed, or only in a slight degree, when the 

 intra-polar conductor is organic, or, in other words, is a bad con- 

 ductor. Thus I have passed a continuous current from my pile, 

 for twenty or thirty minutes, through the upper limbs, the hands 

 being placed in basins of water, and each hand holding an elec- 

 trode, without the current being much enfeebled after the operation. 

 •For medical uses the importance of this fact is manifest. 



One of the greatest inconveniences attending a Daniell's pile, 

 especially for medical purposes, is that it exhausts and tarnishes 

 itself in repose nearly as much as in action. Fifteen elements of 

 my Daniell's pile had been at work for three weeks, for the ap- 



' Z, zinc. C, carbon collector. D, porous cell containing the protosnlphate of 

 mercury. V, external vessel. 



