62 



BIOLOGY: GENERAL AND MEDICAL 



the effect of the current is to alter the position of the 

 cilia at the kathodal end or side, so that the organism 

 changes its direction and swims backwards. 



If the experiment is performed with water containing 

 both ciliates and flagellates, the electrotropic reaction 

 is found to be different for the two kinds of organisms. 



FIG. 14. Electrotropic reaction of Paramoecium. The lower figure shows the 

 mode of applying the electric current, the upper a microscopic field showing the 

 migration of the organisms from the + to the pole. (Verworn.) 



The ciliates, as has been shown, tend toward the kathode, 

 but the flagellates tend toward the anode. 



The most active responses to electrical stimuli appear 

 in animals possessed of a nervous system, by which the 

 activity of other parts of the body is dominated. All 

 nervous tissue seems to be highly susceptible to elec- 



