" Royal Society, 311 



tube passed from the tube into a measured bell -jar over mercury. 

 The oxygen which the substance contained, besides that which 

 was there combined with nitrogen as binoxide of nitrogen, was 

 estimated by its oxidizing action on protosulphate of iron. 



The analytical results led to the formula 2 SO 3 + HO + NO 3 , 

 the analysis having given a slight excess of sulphuric acid and 

 of water. The formula may be written S0 3 HO + S0 3 N0 3 , 

 which is a compound of hydrated sulphuric acid and anhydrous 

 sulphuric and nitrous acids. 



By the action of anhydrous sulphuric acid and hyponitrous 

 acid, gas is disengaged, and a white hard crystalline compound 

 of high specific gravity is obtained which has approximately the 

 composition 2 SO 3 + NO 3 , and is therefore the anhydrous com- 

 pound. Treated with water, brown vapours are evolved, and 

 the distillate has approximately the formula 3 SO 3 + NO 3 . 



XLII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 240.] 



Jane 20, 1861. — Major-General Sabine, R.A., Treasurer and Vice- 

 President, in the Chair. 

 rpHE following communication was read : — 

 -*• "Electro-Physiological Researches. — Eleventh Series. On 

 the Secondary Electromotor Power of Nerves, and its Application to 

 the Explanation of certain Electro-Physiological Phenomena." By 

 Professor C. Matteucci. 



The object of this paper is to show by experiment that when a 

 nerve is traversed by an electric current, it acquires in all its points 

 a secondary electromotor power, and consequently becomes capable 

 of producing in a conducting homogeneous circuit, whose extremities 

 touch any two points of that nerve, an electric current in an opposite 

 direction to that of the original current. This result is independent 

 of the vital properties of the nerves, but is affected in greater or less 

 degree by their physical condition. A similar effect indeed is pro- 

 duced by the passage of an electric current in all porous substances 

 imbibed with a conducting liquid, and the phenomenon has been 

 studied in its generality by other physicists ; but the purpose of the 

 present paper is to determine the conditions of the secondary electro- 

 motor power of nerves, in order to make a due application of these 

 conditions to the explanation of the phenomena exhibited by nerves 

 on the opening of a voltaic circuit which has traversed them. 



Having explained the object of his memoir, the author, before giving 

 an account of his experiments, proceeds to describe certain improve- 

 ments he has lately made in the instruments he employs for electro- 

 physiological researches, whereby he is able more easily and effec- 

 tually to avoid the risk of disturbing currents liable to be produced 

 in the apparatus itself. 



The fundamental experiment on which the main position of the 



