Mr BAXTER, ON ORGANIC POLARITY. 253 



important experiments on the separation and transfer of chemical agents by means of the 

 voltaic apparatus, which was in the autumn of 1806, I was forcibly struck with the probability 

 that animal secretions were effected by the agency of a similar electric power ; since the 

 existence of this power in some animals was fully proved by the phenomena of the Torpedo 

 and of the Gymnotus Electricus ; and since the universal prevalence of similar powers of 

 lower intensity in other animals was rendered highly probable by the extreme suddenness 

 with which the nervous influence is communicated from one point of the living system 

 to another. 



" And though the separation of chemical agents, as well as their transfer to a distance, and 

 their transition through solids and through liquids which might be expected to oppose their 

 progress, had not then been effected but by powerful batteries ; yet it appeared highly pro- 

 bable that the weakest electric energies might be capable of producing the same effects, though 

 more slowly in proportion to the weakness of the power employed, 



" I accordingly at that time made an experiment for the elucidating this hypothesis, 

 and communicated it to Mr Davy and to others of my friends. But though it was conclusive 

 with regard to the sufficiency of very feeble powers, it did not appear deserving of publication 

 until I could adduce some evidence of the actual employment of such means in the animal 

 economy. ^ ^ « ' ♦ 



" The experiment was conducted as follows : I took a piece of glass-tube about three- 

 quarters of an inch in diameter, and nearly two inches long, open at both ends, and covered 

 one of them with a piece of clean bladder. Into this little vessel I poured some water, in 

 which I had dissolved ^iru^ °^ ^^^ weight of salt; and after placing it upon a shilling 

 with the bladder slightly moistened externally, I bent a wire of zinc, so that while one 

 extremity rested on the shilling, the other might be immersed about an inch in the water. 

 By successive examinations of the external surface of the bladder, I found that even this 

 feeble power occasioned soda to be separated from the water, and to transude through the 

 substance of the bladder. The presence of alkali was discernible by the application of red- 

 dened litmus-paper after two or three minutes, and was generally manifested even by the test 

 of turmeric paper before five minutes had expired. 



" The efficacy of powers," continues Wollaston, " so feeble as are here called into action, 

 tends to confirm the conjecture that similar agents may be instrumental in effecting the various 

 animal secretions which have not yet been otherwise explained." 



There is one circumstance connected with Wollaston's conjecture which must be noticed, 

 viz. the idea that secretion depended upon, or is the effect of a power similar to that which 

 exists in a voltaic circle; but it must be borne in mind that the origin of the power in the 

 voltaic circle was not so completely understood at the time Wollaston published his conjecture 

 as it is at the present day ; and, although he himself was an advocate for the opinion that 

 it depended upon chemical action, it nevertheless required the elucidation that it has subse- 

 quently received at Faraday's hands; the fact being that the chemical action which occurs is 

 the cause of the power, or, in other words, the current is a mere manifestation of the chemical 

 action that is taking place. I shall now pass on to the consideration of the manifestation of 

 current force during secretion in other organs ; and first, in the liver. 



