MUSCLES, NERVES, AND ELECTRICAL ORGANS. 189 



upper half of the muscle the left, and in the lower half the right 

 term is the greatest. Naturally this can occur from many com- 

 binations of positive and negative alterations of the four terms, 

 upon two of which, however, we must especially fix our attention. 

 It is either PT^Pt or n^lITt ; the upper sign applies to the upper, 

 the under one to the lower half of the muscle. What is actually 

 the case will be decided further on with some amount of pro- 

 bability. 



A remarkable fact which is also expressed in the table, is the 

 greater strength of all secondary actions in the lower half of the 

 muscle. Neglecting the negative preliminary deflections, the sum 

 of these actions in the upper half amounts to 776 SC , that in the 

 lower half to I34i sc . The corresponding numbers for the primary 

 current are 1453 and I434 8C . The difference of the secondary 

 actions is not explained by the downward tapering form of the 

 semi-membranosus, for I have observed it also in the symmetrically- 

 formed gracilis. With the electrodes of the galvanometer applied 

 symmetrically to the group of muscles, one would expect to obtain 

 with alternately ascending and descending polarising-current, a 

 stronger positive polarisation in a descending than in an ascending 

 direction. This I in fact observed in January, 1857, with less 

 perfect apparatus indeed, but with sufficient distinctness. 



The observation is important, that in the series of experiments 

 here described, when they lasted long their result became uncertain, 

 and finally often became opposite ; so that, for instance, in the 

 upper half of the muscle not only is the descending positive 

 polarisation stronger, but negative polarisation appears .even with 

 an ascending primary current. Finally, one circumstance deserves 

 to be mentioned which comes out so distinctly in the table that I 

 must consider it as unquestionable in spite of its paradoxical 

 nature. With very strong descending currents the polarisation in 

 the whole group of muscles becomes positive again after the critical 

 time of closure, which is as usual marked by deflections in oppo- 

 site directions. With 20 Groves there was only at first a trace of 

 this condition ; with 30 Groves it was stronger ; with 40, however, 

 so distinctly marked that with an ascending current and times of 

 closure respectively, 20", i', 5'. I obtained deflections of 125, 

 112, I7o sc ; with a descending current, +165, + 166, -|-ii7 sc . 

 Whether this is connected with different polarisability of the 

 two halves of the muscle in both directions, and how it is so, is 

 still quite obscure. In order to embrace the relation in Fig. 5, 



