380 



ELECTRO-PHYSIOLOGY 



CHAP. 



apparent contradiction, while du Bois-Beymond (whose inter- 

 pretation of the negative variation in the muscle current will 

 be discussed below) finds himself reduced to the highly 

 improbable assumption that the natural, uninjured ends of 

 fibres, or parelectronomic layer of the same, take little or no 

 part in the excitatory process. 



Against this, it must be remarked in the first place that a 

 tetanic action current in the same direction may always be 

 observed when the ends of fibres are not included in the 

 leading-off tract, any two points in the longitudinal surface of 

 the muscle being taken as the contacts of the leading-off 



M 



FIG. 120. Schema of the diphasic action current. (Bernstein.) 



circuit (Hermann, 27). The cause of this may be determined 

 by an experiment first carried out by Bernstein (I.e. p. 1.60 ff.) 

 with the aid of the rheotome ; it is also valuable in other 

 connections. 



Let (M, M} be a regular muscle with parallel fibres, at one 

 end of which single stimuli are led in at equal intervals by the 

 rheotome (Fig. 120), while between every two excitations there 

 is a very brief closure of the galvanometer circuit at any con- 

 venient moment of the pause between the excitations ; then if 

 excitation and galvanometer closure occur simultaneously no 

 result can follow, since the wave of excitation, starting from 

 (P), requires a certain time to reach the nearest leading-off 

 point (a). But if the galvanometer circuit is always closed at 



