422 



GENERAL PHYSIOLOGY 



experiments on the stimulation of nerves that are in the electrotonic 

 condition have shown that upon the making of the current the 

 irritability rises at the kathode in comparison with the normal, 

 but at the anode is depressed ; this relation is completely reversed 

 upon breaking, so that for a short time after breaking an increase 

 of irritability at the anode and a decrease at the kathode are 

 noticeable. Thus, opposite processes exist at the two poles upon 



making, and each is reversed 

 upon breaking. Whether 

 similar relations between the 

 effects of making and break- 

 ing on the one hand, and 

 those of the two poles on the 

 other, will be discovered in 

 many free-living cells, later 

 experiments must show. But 

 that the opposition in the 

 effects at the two poles upon 

 making, which exist in muscle 

 and nerve, is not to be gene- 

 ralised for all living substance, 

 is shown by the simple fact 

 that in Actinosphcerium, Or- 

 Mtolites, and Amphistegina, it 

 is not present ; in these forms 

 an excitation of contraction 

 alone appears at both the 

 anode and the kathode. 



In summarising briefly our 

 knowledge of the polar effects 

 of the galvanic current, it can 

 only be said that the primary 

 effects of the constant current 

 are localised at the points of 

 entrance into (anode) and exit 

 from (kathode) the living sub- 

 stance ; in the different forms 

 of living substance the kind 

 of excitation at the kathode 

 and at the anode upon making and upon breaking are very 

 different ; hence, no general law of polar excitation, applicable to 

 all living substance, can be formulated. 



We will here leave the polar effects of the galvanic current and 

 take up the various kinds of excitation-phenomena caused by 

 electric stimulation. The effects upon contractile substances have 

 already been considered to some extent. Contractile effects that 

 are manifested outwardly in motion will now be examined. 



FIG. 203. Tradescantia virginica. A cell from a 

 stamen-hair. A, Unstimulated ; , stimulated 

 by an induction-current. The protoplasm has 

 flowed together into globules and lumps at 

 a,b,c,d. (After Ktthne.) 



