310 ELECTRO-PHYSIOLOGY CHAP. 



study, it is allowable to suppose that the proposition laid down 

 above with reference to the electrical excitation of protozoans holds 

 good for the great majority of the forms hitherto investigated, 

 thus establishing in their case a peculiar and unquestionably very 

 remarkable opposition to the phenomena of muscular elements in 

 general, as well as of nerve. The allied assumption that the law 

 of polar excitation, according to Pflliger, holds good without 

 exception for all excitable protoplasm, thus appears to be finally 

 disposed of. 



The interesting observations of Eoux (-48) upon "morpho- 

 logical polarisation" of ova are germane to the phenomena 

 described in the foregoing pages. In order to determine whether 

 the electrical current was capable of influencing the direction of 

 the first cleavage of the ovum, Eoux submitted a strip of frog's 

 spawn about 4 cm. long, with fertilised ova, to the action of an 

 alternating current of 100 volts potential, intended for lighting- 

 purposes. In about ten minutes a transverse furrow dividing 

 the egg into two equal parts appeared in each egg, the furrow 

 being everywhere at right angles to the direction of current. 

 Even before this happens a distinct partition of the surface into 

 three fields is noticeable, divided off by two parallel circular 

 boundary lines, an equatorial girdle without visible alteration, 

 and two polar area? opposite the electrodes, with an altered and 

 coloured surface. If instead of a single band of spawn a simple 

 layer covering the bottom of a round vessel is submitted to the 

 action of the current, the electrodes being placed at its two 

 opposite margins, the equatorial girdle of the entire series of 

 eggs, or, more precisely speaking, the boundary lines between 

 it and the polar zones, form curves which all begin at right 

 angles to a straight line, between the electrodes (Fig. 100), and 

 then sweep round the nearer electrode, gradually increasing their 

 distance from it as they approach the wall of the vessel, to end 

 at right angles to the same. 



The amount of curvature is at its maximum close to the 

 electrodes, and gradually diminishes up to the middle line, at 

 right angles to the current axis. The merest inspection shows 

 us that we are here dealing with lines of equal potential, or the 

 equipotential surfaces of the whole electrical field marked out 

 by these. In the ova corresponding with a single line of 

 potential, the breadth of the equatorial surface increases with 



