406 MUSCULAR MOTION. 



Jaid down by M. Ampere, that two currents attract each other when 

 they move in the same direction. The living muscles are, consequently, 

 regarded by them as galvanometers, and galvanometers of an extremely 

 sensible kind, on account of the very minute distance and tenuity of 

 the nervous filaments. They moreover affirm, that, by anatomical ar- 

 rangement, the nerve is fixed in the muscle in the very position required 

 for the proper performance of its function; and they esteem the fatty 

 matter, which envelopes the nervous fibres, and which was discovered 

 by M. Yauquelin, as a means of insulation for preventing the electric 

 fluid from passing from one fibre to another. 



Soon after hearing of M. Ampere's discovery of the attraction of elec- 

 trical currents, it occurred to Dr. Roget, 1 that it might be possible to 

 render the attraction between the successive and parallel turns of heli- 

 acal or spiral wires very sensible, if the wires were sufficiently flexible 

 and elastic ; and, with the assistance of Dr. Faraday, his conjecture 

 was put to the test of experiment in the laboratory of the Royal Insti- 

 tution of London. A slender harpsichord- wire, bent into a helix, being 

 placed in the voltaic circuit, instantly shortened itself whenever the 

 electric stream was sent through it; but recovered its former dimensions 

 the moment the current was intermitted. From this experiment it was 

 supposed, that possibly some analogy might hereafter be found to exist 

 between the phenomenon and the contraction of muscular fibre. 



The views of MM. Dumas and Prevost were altogether denied by 

 M. Raspail, 2 on the ground, that it is impossible to distinguish, by the 

 best microscope, the ultimate muscular fibre from the small nervous 

 fibrils by which those gentlemen consider them to be surrounded loop- 

 wise. He farther affirmed, that the zigzag form is the necessary result 

 of the method in which they performed their experiments, and is 

 produced by the muscular fibre adhering to the glass on which it was 

 placed. His own idea, founded on numerous observations, is, that the 

 contraction of the fibre in length is always occasioned by its extension 

 in breadth under the influence of the vital principle. Independently, 

 however, of M. Raspail's objection, the circumstance, that, in this mode 

 of viewing the subject, the muscle itself is passive, and the nerve alone 

 active, is a stumbling-block in the way of the views of MM. Dumas and 

 Prevost, and of Dr. Roget. It is proper, too, to remark, that M. Person 3 

 was unable to detect any longitudinal galvanic currents in the nerves 

 by the most sensible galvanometer ; and that other stimuli besides 

 galvanism are capable of exciting the muscular fibre to contraction. 

 This we daily see in experiments on the frog, by dropping salt on the de- 

 nuded muscle. Prof. Miiller 4 hence infers, that a nerve of motion, dur- 

 ing life, and whilst its excitability or irritability continues, is so circum- 

 stanced, that whatever suddenly changes the relative condition of its 

 molecules excites a contraction at the remote end of the muscle, and 



1 Electro-Magnetism, p. 59, in 2d vol. of Nat. Philosophy, Library of Useful Knowledge, 

 London, 1832. 



3 Chimie Organique, p. 212, Paris, 1833. 



3 Journal de Physiologie, torn. x. Paris, 1830. 



4 Art. Electricitiit (thierische) in Ericyclopad. Worterb. der Medicin. Wissensch., x. 545, 

 Berlin, 1834. 



