iv ELECTROMOTIVE ACTION IN MUSCLE 353 



off points in the series mentioned, and the positive current 

 always flows through the external circuit from the point nearest 

 the positive end of the series to that which is nearest the 

 negative end. This is the law of all vital currents in nerve and 

 muscle. 



" A sartorius exposed with all possible precaution, e.g. 

 that is no longer normally nourished, undergoes a slow and 

 steady descending alteration, because dissimilation preponderates 

 over assimilation ; it is slowly dying. 



" If this descending change proceeds in every part at exactly 

 the same rapidity, the most sensitive galvanometer will fail 

 to detect any current. This ideal case is never of course 

 fully realised. But with even a moderately sensitive galvano- 

 meter, no current will be detected in such a muscle, as was 

 shown by du Bois-Eeymond, as well as later observers. On 

 making a cross-section in the muscle, a more rapid descending 

 change at once appears in the muscle-substance ; the part im- 

 mediately adjacent to the section mortifies. This dead part 

 is no longer included in the living continuum, and must be 

 regarded as an inessential appendage. The more rapid ' down ' 

 change and mortification, however, proceed pari passu along the 

 fibre, as may be verified under the microscope, and after making 

 a transverse section, there is always a more rapid descending 

 alteration than in the other fibres. The cross-section is therefore 

 negative to the longitudinal surface of the muscle." 



But it is not merely by theoretical considerations, in addi- 

 tion to its extreme simplicity, that the Hermann-Hering theory 

 is distinguished from all others. There are also direct experi- 

 mental facts in its favour, which may be taken as proven. Among 

 these, apart from all previous experiments on the absence of 

 current in uninjured muscles, is that by which Hermann tries to 

 determine the question whether the development of the demarca- 

 tion current, on making an artificial cross-section, takes a percep- 

 tible time, or whether the full value of the P.D. between longi- 

 tudinal and transverse section is reached immediately after 

 injury, as must necessarily be the case under the presumption 

 of pre- existence of electromotive forces. For this purpose 

 Hermann constructed a " fall " rheotome, in which the expansion 

 of the tendo achilles was torn away from the gastrocnemius by 

 a heavy falling body, the galvanometer circuit being simul- 



2 A 



