LIVING MATTER 31 



which it may have thrust out from its body. This 

 property of " irritability " is one of the most remark- 

 able which is possessed by living matter. It was 

 defined by Claude Bernard as being the property 

 possessed by the protoplasm of every anatomical 

 element of being stimulated to activity and of 

 reacting in one particular way to the external stimuli 

 to which it might be submitted. What happens in 

 this case of irritability is that some of the internal 

 energy of the amoeba is transformed from the 

 potential to the kinetic state and that in " response 

 to an action of itself inadequate to produce it ; and 

 has been compared not inaptly to the discharge of 

 a cannon, where foot-tons of energy are liberated in 

 consequence of the pull of a few inch-grains on the 

 trigger, or to an indefinitely small push which 

 makes electric contact : the energy set free is that 

 which is stored up in the charge 'V 



Thirdly, the amoeba may be observed to f eed AssimUatioi 

 and this it does by putting forth processes of its 

 body wherewith it surrounds any particle of food 

 which may be in the water around. Having ac- 

 complished this it then dissolves the particle or 

 such portions thereof as are available for its purpose, 

 utilises the dissolved material for the re-building 

 of its tissues and the replenishment of the energy 

 which it has expended in its various actions and 



1 Hartog. 



