238 RESEARCHES ON SECONDARY ELECTROMOTIVE 



descending-, and vice versa ; for the direction of the current in the 

 first case would have exactly the same significance as regards the 

 first half, as the opposite direction of the current in the second 

 case would have as regards the second half, because being sym- 

 metrical the one half would be the exact reflection of the other. In 

 like manner it would be expected that each individual half would 

 behave in general differently towards the two directions of current, 

 because in each half there would be no symmetry of structure in the 

 up and down direction. 



Du Bois-B/eymond's muscle-preparation deviates widely from the 

 strictly symmetrical muscle scheme above described, yet there is 

 an essential analogy, in so far as there are tendinous intersections 

 passing through the middle of both muscles, and as the pair of 

 muscles taper away above and below. The result of du Bois-Rey- 

 mond's experiments does not therefore surprise us at all, whilst 

 to him it appeared striking and of great import. 



The same thing may be said as to the further observation of du 

 Bois-Reymond, that the strength of the secondary electromotive 

 actions in both halves of the pair of muscles (or even in the gracilis 

 alone) was not equal. The simple reason of this is, that the two 

 halves of the muscle are not exactly symmetrical in relation to 

 the equator ; the tendinous intersections do not lie in the equator 

 itself, nor is the configuration of the upper half of the pair of 

 muscles (or of one of them) the exact reflection of the lower. More- 

 over there could scarcely be a muscle adapted to this kind of re- 

 search, of which both the external and internal structure would be 

 strictly symmetrical. We should only have been surprised if du 

 Bois-Reymond had found the strength of the secondary electro- 

 motive phenomena to be always equal in the two halves of the 

 muscle, whereas the opposite result is what might have been antici- 

 pated. 



In answer to the final point emphasised by du Bois-Reymond, 

 that when the galvanometer electrodes are placed symmetrically on 

 the muscle, so that one is below the upper stimulating electrode, 

 the other above the lower one, the polarisation-currents are not 

 equal in both directions, it must also be said that it would be 

 strange if they ever were equal. So long as we start with the 

 assumption of an internal polarisation of the whole tract through 

 which the stimulating current flows, all inequalities of polarisation 

 dependent on the direction of the stimulating current, must con- 

 tinue to afford new and enigmatical problems. 



