THE PKODUCTION OF ENERGY IN MUSCLE 103 



The Character of the Electrical Variations in Muscle. Current 

 of Injury and Current of Action. If a perfectly normal resting muscle 

 is connected with two non-polarizable electrodes which in turn com- 

 municate with a galvanometer, the indicator of this instrument re- 

 mains perfectly stationary. The reason for this is that an uninjured 

 and inactive muscle is isoelectric, i.e., it does not present differences 

 in electrical potential which could give rise to a current (Hermann). 

 This condition, however, does not prevail if a muscle is isolated in the 

 usual way and is then removed from the body, because it is scarcely 

 possible to do this without injuring it. On being connected with a 

 galvanometer, such a muscle immediately deflects the needle, because 

 it is no longer isoelectric. A current is set up in consequence of these 

 differences which, in accordance with the direction of the deflection 

 of the galvanometric indicator, passes from the unin juried to the in- 



FIG. 58a. THE CURRENT OF INJUBT. 

 M, muscle; G, galvanometer; J, seat of injury. 



jured portion of the muscle (Fig. 58). Viewed from the outside, there- 

 fore, the uninjured portion of a muscle is positive (anode) and the 

 injured portion negative (cathode). But inside the muscle, the current 

 passes from the injured portion to the uninjured, so that the former 

 constitutes its positive and the latter its negative pole. Most com- 

 monly, however, we characterize this current as galvanometrically 

 negative, because notice is taken only of its direction outside the 

 muscle. 1 This current" is usually referred to to-day as the] current 

 of injury, although Hermann has called it the demarcation current, 

 and Matteucci, 2 the current of rest. The latter designation has its 

 origin hi the fact that the resting muscles of the thigh of the frog yield 

 an electrical current whenever they are cut across transversely and 

 connected with a galvanometer. A few years later, however, Du- 

 Bois-Reymond 3 proved that resting muscles are isoelectric and that 

 the current of rest is really a current of injury. 



1 Biedermann, Ergebn. der Physiol., ii, 1903, 173. 



2 Transact. Acad. des sciences de Paris, 1838-42. 



3 Unters. viber tier. Elektrizitat, Berlin, 1848. 



