THE MANIFESTATIONS OF LIFE 63 



trical conduction and stimulation, so that the applica- 

 tion of an electrode to the central end of a motor nerve is 

 followed by immediate muscular contraction; to the 

 central end of a secretory nerve by secretion on the part 

 of the glands governed by the nerve, and to the periph- 

 eral end of a sensory nerve by painful sensations. 



The facility with which electric currents are trans- 

 mitted by the nerves has led to the assumption by many 

 that electricity and nerve force are identical. 



In the transmission of electric currents along the 

 nerve fibres there is a difference in degree only between 

 anodal and kathodal stimulation. 



Loeb transmitted an electric current through a trough 

 of water containing an Amblystoma and found that a 

 secretion of sticky white mucus appeared upon the 

 skin wherever it was struck by the current waves ema- 

 nating from the anode. 



Currents of considerable intensity produce cytolysis 

 or disintegration of the protoplasm probably by trans- 

 formation of the electrolites of the contained salts. 

 Kiihne found that when a rhizopod known as Actino- 

 sphserium was subjected for some time to a constant 

 current, it began to disintegrate upon the anodal side. 



Currents of high intensity passed through the higher 

 animals cause death from destruction of the nervous 

 system. It is in this way that men are killed by con- 

 tact with "live" trolley wires and by electrocution. 



GEOTROPISM OR RESPONSE TOWARD THE FORCE OF 

 GRAVITY. 



The effect of gravity upon living things is pronounced 

 and occasions a variety of reactions. It seems to be 

 more clearly manifested among the vegetable than 

 among the animal organisms because of the greater 

 freedom of movement of the latter, but gravitation 

 reactions, such as maintaining the equilibrium, are to be 

 found among the very highest animals. 



