MUSCLES, NEBVES, AND ELECTRICAL ORGANS. 191 



very strong- current destroys polarisability. This would explain 

 why a maximum of negative polarisability appears the earlier the 

 greater the density of the current. However this may be, I have 

 in my note-book cases where, in spite of the destruction of polarisa- 

 bility by a strong current, the muscle still contracted. From the 

 incompleteness of my former experiments, I am, however, not sure 

 of these things, and I simply mention them now to show how 

 much has yet to be investigated. 



Between saline solution and muscle, positive polarisation is de- 

 veloped in the same manner as between this solution and other 

 animal tissue (Sect. 4). A slice of beef in which the current only 

 reaches a moderate density gives between saline pads only positive 

 polarisation, but a long thin strip gives polarisation in successively 

 opposite directions, or slight purely negative polarisation, for then 

 the internal negative polarisation makes its appearance along with 

 the external positive polarisation. 



We have seen above (Sect. 8) that the limbs of a living frog 1 

 are capable of internal positive polarisation. I early tried similar 

 experiments on living men. In the years 1845 and 1846 I pro- 

 cured a powerful voltaic pile of the very earliest fashion consisting 

 of 150 zinc-copper double plates. Of these, 100 pairs were circular 

 having a diameter of i", 5 were square being z\" long each side. 

 When the pile was used, disks of paper pulp steeped in a warm 

 tolerably strong solution of chloride of ammonium, were employed 

 as moist conductors to lay between the plates. With the last zinc 

 plate a copper plate was connected, and with the last copper 

 plate a zinc one, each of which was dipped in a basin with 

 saturated solution of salt. The equality of the two forefingers 

 with regard to their electrical condition was first tested by dipping 

 them in the conducting vessels of the multiplier. Of course I met 

 here with the same difficulties as in the experiments on negative 

 variation through voluntary tetanus l difficulties which have since 

 been overcome by the method of compensation. The index fingers 

 were now dipped in the basins connected with the battery in order 

 to receive the shock, and immediately transferred to the conducting 

 vessels in order to observe the secondary electromotive action. The 

 shocks of the battery were no trifle. When received with the whole 

 hand they were felt up to the shoulder, and during the time 



1 Monatsberichte der Akademie, 1852, p. in; Moleschott's Untersuchungen 

 zur Naturlehre des Menschen u. der Thiere, 1857, v l- " P- 2 47 J Untersuchungen 

 iiber thierische Elektricitat, vol. ii. part ii. pp. 186 ff. 



