256 Me BAXTER, ON ORGANIC POLARITY, 



and at each of the electrodes. If the direction of the current consequent upon secretion coincide 

 with those that occur at the electrodes, then an increased effect upon the needle is necessarily 

 produced ; but if these currents tend to go in opposite directions, then the result upon the 

 needle will be merely the differential effect. Hence we should be led to very erroneous con- 

 clusions judging merely from the effect upon the needle, either as to the force of the current 

 or its origin. 



Sufficient evidence has been obtained to warrant the following deduction, viz. that when the 

 electrodes of a galvanometer are brought into contact, one with the urinary secretion and the 

 other with the venous blood from the same part, an effect upon the needle occurs indicating the 

 blood and the urine to be in opposite electric states. 



It may just be remarked that slight effects may be observed when the electrode is in con- 

 tact with the arterial blood instead of the venous blood the other being in contact with the 

 urine. But no effects are obtained when one electrode is inserted into the vein and the other 

 into the artery of the kidney. 



Whilst upon the subject of urinary secretion I may allude to a circumstance of some 

 interest. At the time the original experiments were performed it was frequently observed 

 that the blood continued to indicate its positive condition, long after the secreting process could 

 have been going on, which led to the belief that the blood might have the power of retaining 

 iti= peculiar electrical state. Subsequent experiments have tended to confirm this opinion, but 

 it was never supposed that the secretions could have the power of retaining their peculiar 

 electrical condition, until lately. Reading over some of the Memoirs published at the time 

 of the celebrated controversy between Galvani and Volta, I was much gratified by accident- 

 ally finding the following interesting document. It is of some value inasmuch as it is a letter 

 written by Vassali Eandi, at that time one of the celebrated professors at Turin, to 

 M. Delamethrie, then secretary to the Royal Academy of Paris, who requested his opinion 

 *^upon galvanism and the origin of Animal Electricity*." The position that these two 

 individuals held might be adduced as giving some weight to their authority. Amongst other 

 arguments that Vassali Eandi brings forward in favour of the existence of Animal Electricity 

 is the following: " J'ai prouve ailleurs," says Vassali Eandi, "que les urines donnent una 

 electricite negative, et j'ai fait voir plusieurs fois aux D. Gekki, Garotti et aux eleves de 

 medecine et de chirurgie, que le sang tire des veines donne dans mon appareil electrometrique 

 (decrit dans le Vol. V° de 1' Academic des Sciences de Turin, Dec. 19, 1790) une electricite 

 positive." 



It need scarcely be stated that the galvanometer was not then known, and that the effects 

 observed by Vassali Eandi were tnose of attraction and repulsion. Although the results 

 obtained by Vassali Eandi may be supposed to be due to other circumstances, such as 

 evaporation or chemical action, than those arising from Animal Electricity, nevertheless, as 

 recorded facts, they are of some value, inasmuch as they tend to establish similar conclusions 

 which have been arrived at by different modes of investigation, and entirely independent of 

 each other. 



* Journal de Physique, T. XLViii. p. 336, 1799. Oeiminal an. vii. Lettre de Vassali Eakdi & J. C. Delametbrie 



Sur le galvanisme et sur I'origine de rklectricite. animate. 



