416 



THE PROPERTIES OF STRIPED MUSCLE. 



the variation, i.e. the galvanometric effect, as observed with the aid of 

 the rheotome, is diphasic. During the exceedingly short period that 

 the wave is under the electrode I 1 , a current from I 2 to I 1 passes 

 through the galvanometer. During the similar period that it is under 

 the electrode / 2 , a current flows in the opposite direction. If we accept 

 Bernstein's estimate of the rate of propagation and of the duration of 

 the wave, and assume the electrodes to be over 2 cms. apart, there will 

 be an interval of time between the two periods during which there will 

 be no current either way. It will be seen further on that the excitatory 

 change lasts longer than Bernstein supposed. 



In a muscle truncated at one end. with the electrode I 1 on the injured 

 part, the case is different. The variation has one phase only. The 

 wave, as in the other case, makes its way along the fibres, but on 

 its arrival at the injured part it is suppressed, so that its presence there 

 is without galvanometric effect. Consequently, in the injured muscle, 

 from the moment that the excitatory change has ceased at the electrode 

 I 1 the variation is at an end. Hence the whole monophasic variation of 

 the injured muscle represents the first phase of the diphasic of the 

 uninjured. 



FIG. 227. Progress of the wave of excitation, according to Bernstein. 



From Bernstein's description of the single excitatory variation, 

 founded on his observations with the rheotome, we may pass to Her- 

 mann's more recent (1893) account of the same phenomenon, based on 

 a different method of using the same instrument. This method is of 

 such importance that it must be shortly described. 



From the description of the rheotome given above, it will be seen that 

 during each observation of the series, i.e. during each period of excitation 

 of the muscle, the time - interval between excitation and the beginning 

 of the " closing time " remains unaltered. For the better understanding 

 of Hermann's method, let it be supposed that the excitation is continued 

 for a period of two seconds, that this period is divided into ten equal 

 parts, and that at the end of each part the interval between excitation and 

 closure of the galvanometer circuit is increased by T (j%^ second. It is obvious 

 that during each successive part or period of i second, the difference of 

 potential between the leading-oif electrodes represents that which actually 

 exists during the corresponding period of ^y- second, and that if the ten 

 measurements were arranged on an abscissa! axis, the ordinates representing 

 relative negativity of the proximal electrode being directed upwards, those 

 representing relative positivity of the same electrode downwards, and the ends 

 of the ordinates joined, we should have a graphic representation of the 



