

186 SECONDARY ELECTROMOTIVE PHENOMENA IN 



But even when the battery-electrodes are applied to one and the 

 same half of the group of muscles, we cannot be sure that the 

 primary current is equally strong in both directions. As is well- 

 known, there is no such law of reciprocity for electric currents as 

 there is for rays of light. The same electromotive force, acting in 

 opposite directions through the same series of conductors, often 

 generates currents of very different strengths. The necessity of 

 seeing clearly into the conditions of the irreciprocal conduction of 

 electric currents gave occasion to some experiments of von Beetz 

 and myself, which again were the germ of Professor Christiani's 

 thorough investigation of this subject 1 . I have convinced myself 

 that a perfectly sufficient reciprocity of conduction occurs through a 

 clay rod through which the current is led as through a muscle. 



This general experience must not, however, be depended upon, 

 but care must be taken to note the strength of the primary current 

 along with that of the secondary. Professor Georg Quincke, 

 then still in Berlin, had the great kindness to help me with the 

 older observations of this sort, while latterly Professor Christiani 

 aided me, to whom I owe my warmest thanks for his assistance 

 in the present organization of my experiments. 



The following table gives an idea of the great differences which 

 exist between the two halves of the muscle. It is to be under- 

 stood that one of the galvanometer electrodes is applied close to 

 the equator of the group of muscles, and the other invariably either 

 over the under, or under the upper battery-electrodes. 



TEN GKOVES. TIME OF CLOSURE c/'^so. 



1. Upper Half. 

 Muscle current: i89 sc , 2i cgr | . 



S T + ii3 8C | + 93 t +145 I + 81 T +159 I + 6 4 

 P | i7i<> c | 169 j 153 | 159 | 180 i 190 



2. Under Half. 

 Muscle current : 2I4 80 , 22-5^ f . 



b I +294 +i99 



PI 200 | 160 j 160 | 169 j, 185 | 180 



3. Upper Half repeated. 

 Muscle current : 264", 27 c r J. 

 I S I + 34 t + 87 



P| 2IO I 22O 



1 Arthur Christiani, Beitrage zur Elektricitatslehre ; Uber irreciproke Leitung 

 elektrischer Strb'me, Berlin, 1876. 



