MUSCLES, NERVES, AND ELECTRICAL ORGANS. 207 



the same observation holds good as for the two halves of a muscle. 

 For strong positive polarisation weak negative polarisation may be 

 substituted in the thesis ; thus we may say that in the motor roots 

 the ascending negative polarisation predominates, in the sensory the 

 descending. When discussing muscles I referred to reasons to be 

 afterwards given, for taking the same view of them which I do of 

 nerves. 



Various circumstances, amongst others the arrival of the West 

 African Malapterurus, compelled me to break off these experiments, 

 and I was only able to resume them twenty-two years later, in the 

 autumn of 1879. I was then furnished with all the apparatus in- 

 vented during the interval, and this time kindly aided by Professor 

 Gustav Fritsch, whose anatomical skill was the more welcome, that 

 in a consignment of Hungarian frogs for which I was indebted to 

 Professor Jendrassik of Pesth, we found no such giants as the waters 

 of the Brandenburg Mark sometimes supplied formerly. This series 

 of experiments also was not completed. It did not seem advisable to 

 continue them during the winter, after the larger frogs had been 

 used. After that I was under the necessity of devoting myself to 

 the editing of Sachs' results. These new observations, however, 

 yielded much that was of importance. First of all, I tested the 

 behaviour of a mixed nerve-trunk by the method of experiment to 

 which the roots were to be subjected. Here no definite difference 

 was apparent between the actions observed when the current was 

 ascending and when it was descending, as the following example 

 shows : 



FIVE GROVES. TIME OP CLOSURE o"-o37. 



Portion of the Sciatic Nerve between the Vertebral Column and the origin of the 

 branches to the Muscles of the Thigh. 



TIME OP CLOSURE, o"-c>3i. Another similar portion. 

 I f-o.5| f-o. 5 I f-o-st f- i | J-o-St |- i | f-o-5 efcc 



1 1 + 23 I 1+15 11 + 21 | 1 + 17 J 1 + 17 |t*xy-{t+ 



Central portion of the nerve. 



T- 5|{- 6Jf- 6 If- 8 T- 5 IJ-ietc 

 I + I8U + I6 | 1+19-51 1+15-5 I +i8. 5 | 1+ 8 



TIME OP CLOSURE o"-o76. 

 Lower portion with the peroneal and tibial nerves. 



iH~ 3| (~ 2 T J- 3 lj- 2 '5tJ-2-5 

 6 | \+i5i 1 + 21-5 I 1+I4-511 + I4 11+15 



