386 



ELECTRO-PHYSIOLOGY 



CHAP. 



a muscle rhombus, and it is tolerably accurate to say that the 

 nerve-ending lies in the middle of each fibre (Fig. 121). But 

 then it follows that all the points corresponding with the upper 

 contacts (a, b), i.e. the thick part of the muscle, must be affected 

 more, and earlier, by the waves of excitation from the nerve-endings 

 (a, /3) than the lower ends of fibres, corresponding with the tendo 

 achilles. Thus there will at first be a descending, and subse- 

 quently a weaker ascending, current of action. " The upper half 

 of the muscle, on the contrary, should vary first in an ascending 

 and then in a descending direction ; here, however, the structure 

 of the muscle is essentially different; the main part of the 

 current (' Neigungstrom ') is prevented by the folds of the upper 



expansion from producing any ex- 

 ternal effect, so that in the first place 

 the abterminal phase of the upper 

 half of the muscle is hardly per- 

 ceptible, and in the second the upper 

 tendon as a whole must be regarded 

 as a lead-off from the longitudinal 

 section. On leading off from both 

 tendons, the effects are consequently 

 not very dissimilar to those with 

 the lead-off from belly and achilles 

 tendon. There is thus no doubt 

 that the first descending phase 

 starts, not from the expansion of 

 the tendo achilles, but from the 



longitudinal section, while the second ascending phase does 

 originate at the achilles expansion" (Hermann). With the 

 corrosion of the latter, the second phase naturally dies out, since 

 the ends of fibres then become negative without it. And this of 

 course applies to tetanus, in which du Bois-Eeymond first observed 

 the descending effect in the currentless gastrocnemius, since, 

 generally speaking, only the algebraic sum of the opposed action 

 currents can be detected. But, owing to the preponderance of 

 the first descending phase, the effect is actually descending. It 

 is unnecessary here to enter into further minutiaB of electro- 

 motive action in the excited gastrocnemius, since no new 

 theoretical data can be expected from it. We need only 

 mention that Matthias (30) has recently (by Hermann's " rheo- 



Fio. 121. 



