i GENEKAL PHYSIOLOGY OF MUSCLE 69 



that living tissues are under special conditions the seat of 

 electromotive forces, which may excite muscular contractions on 

 the closure of non-metallic circuits. 



Direct proof of this was not available till after the invention 

 of the galvanometer by Nobili (1824), when it became possible 

 not only to demonstrate the existence of the comparatively 

 weak currents present in living tissues, but also to measure them. 

 In 1827 Nobili made use of Schweigger's multiplicator to demon- 

 strate the so-called " natural current " of the frog, directed from 

 the foot towards the head. 



On repeating and varying Nobili's experiment in different 

 ways, Matteucci (1838-40) discovered the phenomenon known 

 later as the "current of rest" in muscle. He amputated the 

 thigh of a skinned frog by a transverse incision, and brought it 

 into the circuit of a galvanometer, by applying one electrode to 

 the cut surface and the other to the outer surface of the thigh 

 muscles. On closing the current the galvanometer needle was 



FIG. 42. Matteucci's experiment of secondary contraction and tetanus. 



deflected, showing a current in the muscle from within outwards, 

 i.e. from the cut surface to the natural surface of the muscle, in 

 the galvanometer circuit from the natural to the cut surface. 1 



In 1842 Matteucci communicated to the Academic des Sciences 

 in Paris another discovery, which Biedermann reckons among the 

 most important in experimental physiology. When the nerve of 

 a frog's leg is placed on the muscle of the opposite leg, and the 

 nerve of the latter is excited by certain stimuli, a vigorous primary 

 contraction results in the muscles of this excited limb, accom- 

 panied by a less vigorous secondary contraction in the muscles of 

 the other limb (Fig. 42). 



This observation was the first demonstration of an electrical 

 phenomenon concomitant with the state of muscular activity. 

 Matteucci interpreted it wrongly ; the true explanation was only 

 possible after the law of the current of rest in muscle and its 

 negative variation had been discovered by du Bois-Eeymond (1843). 



1 To avoid the confusion that frequently arises between the current in the 

 outer (galvanometer) circuit and that flowing within the tissue, it might be well, 

 as suggested by Waller, to replace the ambiguous term " negative " (more correctly 

 "electro-positive") by the term "zincative," which would serve as a reminder that 

 the current flows from the excited to the unexcited portion of the tissue, as from 

 zinc to copper in a Daniell cell. Translator. 



