208 SECONDARY ELECTROMOTIVE PHENOMENA IN 



The actions are always in two directions, as is at once evident on 

 the galvanometer, but the first negative deflection is sometimes 

 limited to a scarcely perceptible jerk. The inequalities in the several 

 series depend undoubtedly on the imperfection of the apparatus for 

 regulating- the times of closure and transmission. Taking together 

 all the experiments I have up to this time made on mixed nerves, 

 there appears a slight preponderance of ascending positive polarisa- 

 tion. In descending it seems to decrease, and indeed even to 

 become reversed. However, the experiments are still too imperfect 

 to permit of such a generalisation, at all events no discussion of the 

 question whether this is connected with the proportion in which the 

 two kinds of fibres are contained in the transverse section of the 

 nerve, can be entered on. On comparison of the above series with 

 those on sensory roots a striking difference appears in favour of the 

 suggested law. 



THREE GROVES. TIME OP CLOSURE o".o37. 

 Sensory Hoots. 



tJ~ 2 I I ^t J-i I ^Tf-2 I 8 TJ-i 

 li + 4-5ir 7 ! l + 9l~ 7 ll + 61~ 8 |l + 9 



Hoots reversed. 



TJ- 5l J-8TJ- 5I/-9TJ- 6 | J-9JJ- 5. 

 | l + i3l 1 + 7 I t+13 11 + 9 11 + "1 1 + H1+ '3 



It is remarkable, however, that the motor roots here again 

 yielded a less favourable* result. 



FIVE GROVES. TIME OF CLOSURE o"-oi5. 

 Motor Roots. 



|J- 3tJ- 2 | f- 3tf- 2 II- 3TJ- 3|J- 4|| I{- 2 '5l{~ 3 8 . 

 it + 23 | 1 + 171 1 + 22 I 1 + 20-5 H + 17 I l + ia J l + i6 II | l+i; 1 l + i8 



Up to the mark || the suggested law is pretty clearly expressed ; 

 but for the most part even to this extent such was not the case. 

 I was no more successful with the nerves of the thigh. 



If consequently the law cannofc be considered to be demonstrated, 

 on the other hand it is not yet determined that it does not hold. 

 It is possible that a combination of current density and time of 

 closure which I did not hit upon in my experiments is required, in 

 order to demonstrate it on the motor roots. In order to make 

 further progress we should require a consignment of bull-frogs 

 (B. mugiens or Catesbyana) from North America. So far my 



