MUSCULAE EFFORT. 477 



The same fact may be demonstrated with an ordinary gal- 

 vanometer; but the evidence obtained by the frog's leg, 

 when the experiment is properly performed, is sufficiently 

 conclusive. 



Matteucci constructed out of the fresh muscles from the 

 thigh of the frog, what is sometimes called a frog-battery ; 

 which exhibits these currents in the most striking manner, 

 their intensity being in direct ratio to the number of elements 

 in the pile. To do this, he takes the muscles of the lower 

 half of the thigh from several frogs, removing the bones, and 

 arranges them in a series, each with its conical extremity 

 inserted into the central cavity of the one below. In this 

 way the external surface of each thigh except the last is in 

 contact with the internal surface of the one below. If the 

 two extremities of the pile be now connected with a gal- 

 vanometer, quite a powerful current from the internal to 

 the external surface of the muscle may be demonstrated. In 

 a pile formed of ten elements, the needle of a galvanometer 

 was deviated to from 30 to 40V ' 



Electric currents are observed in all living muscles, but 

 are most marked in the mammalia and warm-blooded ani- 

 mals. They exist, also, for a certain time after death. 

 Artificial tetanus of the muscles, however, instead of intensi- 

 fying the current, causes the galvanometer to recede. If, 

 for example, the needle of the instrument show a deviation 

 of 30 during repose, when the muscle is excited to tetanic 

 contraction, it will return so as to mark only 10 or 15. 

 This phenomenon is observed only during a continued mus- 

 cular contraction, and does not attend a single spasm. 



Muscular Effort. The mere voluntary movement of 

 parts of the body, when there is no obstacle to be overcome 



1 MATTEUCCI, Lemons sur les phenomenes physiques dfs corps vivante, Paris, 

 1847, p. 175, et seq. For a fuller exposition of these interesting phenomena, 

 the reader is referred to the elaborate treatise on physiology, by Prof. Longet 

 (Traite de physiologic, Paris, 1869, pp. 620, 639). 



