THE MOVEMENTS OF ORGANISMS 293 



shall now consider, is primarily responsible for the electrochemical 

 theory of this irritability. 



For our consideration, two electrical phenomena of muscle are 

 important: In activity, that is during the contraction of muscle, 

 electric currents (action currents) develop; the stimulated point in 

 the muscle becomes negative in relation to the remaining fibers which 

 are at rest. The same thing holds true for nerves hi which no external 

 sign of activity is discoverable. 



If, in an excised mollusc muscle, an injured point is united to an 

 uninjured point of the mantle by a wire having a galvanometer in 

 its circuit, the cut surface is negative and the mantle surface is posi- 

 tive. The same electrical phenomena are observed in a resting nerve. 

 This is called the current of rest, or, according to H. HERMAN, the de- 

 marcation current (HERMAN calls the demarcation surfaces the interface 

 between the injured, dead, and the uninjured, living, substance). 



Evidently action current and current of rest are due to the same 

 cause. In his textbook, R. A. A. TIGERSTEDT states the phenomenon 

 as follows : In muscle as in nerve, a stimulated point, or one which is 

 injured in any way, is negative electrically to every other point which 

 at that time happens to be at rest or uninjured. 



Let us consider how we may explain the direction and magnitude 

 of different potentials which occur when muscle contracts. Elec- 

 trical differences in potential arise on every interface between an 

 electrolyte and a pure solvent or one containing less electrolytes. 

 The simplest case is when an acid, e.g., HC1, is limited by pure water 

 then the more mobile positive H ion will rapidly advance and give a 

 positive charge to the water while the acid is negatively charged by 

 the more slowly moving negative Cl ion. This applies to muscle, 

 for lactic acid arises at the point stimulated or injured. 



The electromotive forces which are derived from a circuit of acids 

 and water or crystalloid electrolytes are much smaller than we 

 observe in muscle. 



Wo. PAULI invokes the colloidal properties of the protein ions in 

 explaining the high electric tension which we obtain in muscle or even 

 in the electric organ of the torpedo. 



Protein in general contains an amino acid with many NH 2 and 

 COOH groups. Let us illustrate the development of electromotive 

 forces by the following diagram in which R represents the protein 

 radicle and L the lactic acid radicle : 



OHCO NH 2 + LH OHCO NH 3 L 

 OHCO |< NH 2 + LH = OHCO h? - NH 3 + L 

 OHCO . NH 2 + LH OHCO NH 3 L 



