Ill 



ELECTRICAL EXCITATION OF MUSCLE 



311 



its distance from the straight line between the electrodes, so 

 that the ova in immediate contact with the margin present the 

 least polar zones, and the largest equatorial surface. Bearing 

 in mind the reaction of each single ovum to the alternating 

 current, a certain analogy with the effects above described in 

 Actinosphaerium cannot be disputed, and if two protozoa are 

 conceived of the size of frog's ova, and submitted under similar 

 conditions to the action of the alternating current the middle 

 disc remaining over, when the polar zones had disintegrated, 

 would presumably exhibit an arrangement of the lines of 

 potential, corresponding with the equators of the ova in Eoux's 

 experiment. 



But this conformity 

 further extends to the dif- 

 ference in mode of action 

 at either pole, which of 

 course appears only with 

 uniform currents. At uni- 

 form conditions of experi- 

 ment, there is developed 

 as Eoux pointed out in 

 ripe, unfertilised ova, " a 

 large grayish polar zone, 

 round the positive elec- 

 trode, directed towards tl/e 



anode, extending far be- FIO. lOO.Ova of Frog in vessel of water, traversed by 



yond the middle line of cu n * f 5 01 ! 1 ** e * . st s ! in f 8 ' ^ rkin f the 



* vertical electrodes. Polar fields dark. (Roux.) 



the electrical field, while 



only the two rows of ova lying nearest the kathode had a 

 coloured kathodic polar zone in default of an anodic zone." This 

 last always appears later, and the changes are less than in the 

 positive zones. "With weaker currents, no polar zone appears on 

 the negative side of the ovum. 



If these effects of current cannot be termed direct con- 

 sequences of an electrical excitation of the plasma of the ovum, 

 they do undoubtedly represent a specific reaction of the still 

 Uriiiy, or at least approximately normal, ovum, even when the 

 capacity of development is not necessarily preserved. Eoux 

 was enabled to demonstrate formation of polar zones in masses of 

 freshly extruded unsegmented ova. 



