MUSCLES, NERVES, AND ELECTRICAL ORGANS. 18 1 



Closely connected with experiments on galvanic currents of 

 variable strength and duration, are experiments made with electro- 

 motors, which from their nature produce short sudden shocks. 

 These produce positive polarisation at once. I have not yet found 

 time to pursue this kind of experiment with new means and appa- 

 ratus, and must content myself with citing older results, which are 

 in the 'main correct. 



In December, 1 846, I obtained to all appearance positive polari- 

 sation in the legs of a living frog with a Saxton's machine, the 

 shocks of which could be sent in the same direction by a commu- 

 tator (Stromwender). As this machine 1 , constructed for Dove by 

 Oertling, passed into the possession of the Physiological Insti- 

 tute, I am in a position to control those experiments which 

 were performed with very imperfect knowledge and experimental 

 methods. Under somewhat better conditions, in November, 1855? 

 I observed positive polarisation in the group of muscles with 

 opening shocks of the induction coil. Lastly, as early as December, 

 1846, I observed positive polarisation in frogs which I killed with 

 a heavily-charged Leyden battery having a surface of about 0-31 

 square metres. The muscles looked blood-stained (blutrunstig), and 

 only gave traces of reaction on the application of other shocks 2 . 



9. On the curves of Polarisation in relation to the time 

 after opening the Primary Current. 



The polarisation of muscles can still be studied in relation to the 

 course it takes after the opening of the primary ^current, and this 

 course may be represented by a curve drawn relatively to the time 

 which has since elapsed. This period of time may be called the 

 ' opening time.' In general the positive as well as the negative 

 polarisation appears very persistent. In Sect. 7 I have already 

 alluded to the difficulties which arise each time that one wishes to 

 employ the same muscle for several consecutive experiments. 

 After a muscle has been strongly polarised in a positive direction 

 it may require twenty minutes or more to elapse before it has so far 

 regained its original condition that the alteration may be disregarded. 

 As, besides, without having been polarised, the muscle does not 

 during this period retain its electromotive condition unaltered, it is 



1 Untersuchungen fiber thierische Elektricitat, vol. ii. part i. pp. 398 ff. ; Wiede- 

 mann, Die Lehre vom Galvanismu su. Elektromagnetismus, vol. ii. 2 ed. Braun- 

 schweig, 1874, p. 236. 



2 Untersuchungen, loc. cit. pp. 181, 182. 



