16 THE SIGNS OF LIFE [LECT. 



current " of quiescent muscle and of nerve is diminished when 

 the' muscle contracts or when the nerve is excited ; he called this 

 diminution "a negative variation of the previous current of 

 rest." Hermann then showed that this negative variation of a 

 current of rest (or current of injury) is only a special case of a 

 more general phenomenon, and that active tissue is, properly 

 speaking, negative to resting tissue, quite irrespective of any 

 previous " pre-existing " current. And from the fact that active 

 tissue is negative, and that the action is propagated in muscle 

 and in nerve, physiologists adopted the expression " negativity 

 of action," and spoke of propagation of a wave of negativity in 

 the excitable tissue. And little by little a confusion of thought 

 established itself; the origin of the expression " negativity" was 

 lost sight of, active tissue was spoken of as being " electrically 

 negative " and then " electro-negative " which is clearly wrong 

 in the accepted physical sense of this term. In physical 

 language the negative pole of a voltaic couple is connected with 

 the electro-positive element, the positive pole with the electro- 

 negative element. And when a writer had escaped an actual 

 misnomer, an ambiguity that was even more mischievous to 

 clear thinking became effective ; a state of negativity of action, 

 propagated from active to non-active parts, arouses in the 

 reader's mind the picture of a current directed in the tissue 

 when connected by two points, active and non-active, from former 

 to latter, i.e., from " negative " to " positive." Now this direction 

 is correct, but it is disturbing to one's thought to regard current 

 as directed from negative to positive. And, in point of fact, the 

 language is actually wrong ; the adjectives " positive " and 

 " negative " as used by Faraday refer to the poles, current is of 

 course from positive to negative in an external circuit, positive 

 and negative refer to an external circuit, and should not be used 

 with reference to the internal circuit. It is a misuse of terms to 

 say that current in the tissue is directed from negative to positive 

 pole. The proper thing to say is that direction in the tissue is 

 from electro-positive to electro-negative, that active tissue is 

 electro-positive to resting tissue, that a wave of electro-positivity 

 travels in muscle (or in nerve) from an excited spot. 



But, in the present state of our physiological literature, is it 



