Prof. Matteucci^s Experiments in Electro-physiology. 461 



which pyroxyliue is the type. In the first, hydrogen is replaced 

 by NO' ; and in the last, HO is replaced by NO^. By the action 

 of ferrous acetate on the first, all the nitrogen remains in the 

 new body formed, as when nitrobenzole is converted into aniline. 

 In the case of the second, the nitric acid is converted into am- 

 monia. Bechamp points out that this reaction may serve as a 

 method of determining ammonia, an idea in the execution of 

 which he has been anticipated by M, Ville. 



M. de San Luca found that when about 7000 to 8000 litres of 

 moist ozonized air were passed over potash, nitric acid could be 

 distinctly detected. The air, before being ozonized, was freed 

 from substances held in mechanical suspension, and from nitro- 

 genized substances, by being passed through an apparatus con- 

 taining potash and sulphuric acid. 



LX. Some Experiments in Electro-physiology. 

 By Prof. Matteucci. In a Letter to Dr. Faraday. 



My dear Friend, May 1, 1856. 



I THINK I have already told you that for some time past I 

 have been making experiments in electro-physiology. Allow 

 me now to communicate to you the results of my work. 



I have lately succeeded in demonstrating and measuring the 

 phsenomenon which I have called muscular respiration. This 

 respiration, which consists in the absorption of oxygen and the 

 exhalation of carbonic acid and azote by living muscles, and of 

 which I have determined the principal conditions and intensity 

 compared with that of the general respiration of an animal, has 

 been studied particularly on muscles in contraction. I have 

 proved that this respiration increases considerably in the act of 

 contraction, and have measured this increase. 



A muscle which contracts, absorbs, while in contraction, a much 

 greater quantity of oxygen, and exhales a much greater quantity 

 of carbonic acid and azote, than does the same muscle in a state 

 of repose. A part of the carbonic acid exhales in the air, the 

 muscle imbibes the other part, which puts a stop to successive 

 respiration and produces asphyxy of the muscle. Thus a muscle 

 soon ceases to contract under the influence of an electro-magnetic 

 machine when it is enclosed in a small space of air : this cessa- 

 tion takes place after a longer interval of time if the muscle is 

 in the open aii-, and much more slowly still if there be a solution 

 of potash at the bottom of the recipient in which the muscle is 

 suspended. IMuscles which have been kept long in vacuum or 

 in hydrogen are nevertheless capable, though in a less degree, 

 of exhaling carbonic acid while in contractioii ; this proves clearly 



