364 ELECTRO-PHYSIOLOGY 



to test the current would contract in consequence of the rapid 

 decrease in current at the beginning of tetanus, if the nerve 

 bridged over the longitudinal and transverse sections of the excited 

 muscle. On the other hand, we should hardly look for this result 

 at the end of tetanus, since the muscle only returns gradually to 

 its original condition. This experiment, as tried by du Bois- 

 Reymond, yielded a very striking result, not at all in correspond- 

 ence with what was anticipated. The test-limb, i.e., not merely 

 twitched at the beginning of tetanus, but actually fell into secondary 

 tetanus during the whole of the primary excitation. If this is im- 

 perfect, so that each single twitch remains recognisable, and the 

 muscle is then connected on the one hand with the galvanometer, 

 and on the other with the physiological rheoscope, the latter 

 responds by a secondary twitch to every primary contraction, while 

 the magnet, in consequence of its sluggishness, swings back simply 

 in the direction of the negative variation. We may, therefore, 

 and indeed must suppose that even with the most complete 

 fusion of the visible contractions of the primary muscle, into sus- 

 tained tetanus, each impact of stimulation calls out an excessively 

 short negative variation, distinct in time from that which succeeds 

 it, so that the muscle current fluctuates, as it were, up and down 

 in the rhythm of the tetanising stimulus, by which we see that 

 notwithstanding the apparently steady contraction of the muscle 

 in tetanus, it really originates in discontinuous alterations of 

 state, exhibited more especially in its galvanometric response 

 as above. The extraordinary superiority of the physiological 

 rheoscope to all other known physical apparatus for testing 

 current is obvious, and it is only quite recently that a method 

 has been discovered which (with regard to the possibility of 

 demonstrating variations in current lasting for a short period 

 only, and following in rapid succession) may be compared with 

 the faithful response of the physiological rheoscope to the 

 electrical fluctuations. The accompanying diagram (Fig. 113) 

 gives a clear picture of the behaviour of the muscle current in 

 tetanus as attested from observations on secondary tetanus. 



" If the abscissa (o, t) represents the time, on which the ampli- 

 tude of the current is drawn at each second as ordinate, (o, ) 

 further represents the constant magnitude of the muscle current 

 in the state of rest ; for, in order merely to produce a diminutions! 

 effect in the multiplier, it is indifferent whether (o, .) becomes 



