638 



The Opposite Electrification produced by Animal and Vegetable 



Life. 



By W. M. Thornton, D.Sc, D.Eug., Professor of Electrical Engineering in 

 Armstrong College, Newcastle-upon-Tyne. 



(Communicated by Dr. A. D. Waller, F.R.S. Received June 17, 1910.) 



1. Introductory. — When a steady electric current is passed through a drop 

 of pond scum rich in animal and vegetable organisms, two opposite move- 

 ments of migration of the living cells will in general be observed. Diatoms 

 and unicellular algaj, for example, move towards the negative pole, amoeboid 

 animal organisms to the positive. The clearness of the effect is often 

 confused by the presence of anchored and skeleton cells of either kind, and 

 the case of pond scum is only given because tlie effect to be described was 

 first observed in this way. 



Early in 1904 it was desired to find an indicator for the qualitative 

 detection of voltage gradient in liquids in fields of microsco]_:)ic dimensions. 

 The orientation of long diatoms into line with the current was anticipated 

 from the known behaviour* of bacteria in an alternating field, and found to 

 occur. In steady, that is unidirectional, fields they not only orientate but 

 move along the line of current-fiow to the negative pole. They therefore 

 serve in two ways to indicate the presence of a steady current in the liquid. 



At tlie first, and in all subsequent trials, the. movement of migration of 

 the diatoms was accompanied by one in the same direction of portions of 

 most of tlie vegetable matter free to move, and a simultaneous movement in 

 the reverse direction of the free animal forms, provided that the motile 

 activity of the latter did not overpower the mechanical influence of the field. 

 The movement was quite dead-beat, reversing instantly with the reversal of 

 polarity, and since the only mechanical force an electric field can exert is 

 upon an electric charge it was concluded tliat tlie opposite movement of the 

 cells indicated that they carried opposite charges, the animal cells being 

 negatively electrified, the vegetable cells positively. 



2. Method of Experiment. — To observe the movement it is well to liavo the 

 field as stnmg as possible ; it was found that T'l volts per centimetre was 

 the highest which could be conveniently used. This is much greater than 

 that employed by previous workers, which rarely exceeded 10 volts per 

 centimetre. 



To avoid tioulile l»y lilu'ratiou of gas at the electrodes witli this high 

 * l>. liortct, '(Joini)t('s K(^ihIiih,' April -20, IHOfJ, j). 892. 



