MUSCLES, NERVES, AND ELECTRICAL ORGANS. 193 



take the shock with the forefinger while the secondary electro- 

 motive action was led off by the middle finger. Until the ex- 

 periment has been successful in this or some similar form, it is 

 open to the suspicion that we have here to do with external 

 positive polarisation in the skin, and not with internal polari- 

 sation of the muscles ; on the other hand there is no apparent 

 reason to doubt that the negative deflections observed in these 

 experiments depend upon true internal polarisation, and this new 

 action of the current in the human body appears to me to 

 be in some degree worth the attention of electro-therapeutists. 

 I cannot yet say whether the contraction of the rheoscopic frog 

 produced by polarised human limbs arose from positive or negative 

 polarisation. 



12. Positive internal Polarisation of Muscles in Conflict with 



Tetanus. 



One of the most remarkable relations shown by the internal 

 positive polarisation of muscle is, that it is influenced by the state 

 of activity of the muscle, and in reality a tetanised muscle is 

 capable of less strong polarisation than one at rest. 



The experiment is a difficult one on account of the negative 

 variation which is mixed up with it, which cannot always be 

 estimated with certainty. The galvanometer electrodes must be 

 applied to the group of muscles to which the nerve is left attached 

 in such a manner that the muscle -current is as weak as possible ; 

 then the negative variation is also weak. On account of the 

 asymmetrical construction of the semi-membranosus, a more or 

 less strong ascending current is present when the position of the 

 electrodes is symmetrical (Sect. 7). Hence, we obtain the desired 

 equality by applying the lower electrodes higher up on the muscle. 

 The group of muscles must be so firmly stretched that they do not 

 perceptibly shift on being tetanised. The amount and direction of 

 the remaining variation is noted. We then send a polarising shock 

 of short duration through the group of muscles every minute and 

 a half to two minutes, thus leaving it alternately at rest and 

 tetanised. We regulate the direction of the current so that the 

 negative variation is added to the secondary electromotive action. 

 In spite of this, the action is always less during tetanus than 

 during the repose of the muscle. 



