io8 THE PSYCHIC LIFE 



in view particularly the muscular fibres, and the laws 

 of irritability are only supposed to cover a series of 

 physiological experiments made upon the reaction of 

 a striated muscle. They are not, then, hypothetical 

 laws, but are much rather particular experiments gen- 

 eralized and extended to undifferentiated protoplasm. 

 It is proper to remark here, that we have not as yet 

 been able, by means of direct experiments, to ascer- 

 tain from life the laws of irritability in undifferentiated 

 protoplasm. The experiments made upon this point, 

 for instance, the experiment causing the protoplasm 

 of a detached cell to contract by means of an electric 

 current, have not yet been brought to a precise result; 

 for the structure of protoplasm is so delicate and so 

 complex, that even the slightest excitation suffices to 

 produce an alteration, and since it is difficult to distin- 

 guish the contraction of the protoplasm from its coag- 

 ulation. But we shall pass by this subordinate ques- 

 tion. 



The question now remains, whether the compli- 

 cated experiments made in muscular physiology, which 

 M. Richet generalizes .and extends to the physiology 

 of all cellules, include and comprehend the whole psy- 

 chology of an independent organism, and whether we 

 may say with M. Richet, that irritabilit}' (thus under- 

 stood) represents all of cellular psychology. 



Plainly not. The numerous facts which we have 

 cited in the foregoing essay, transcend the too narrow 

 limits within which it has been attempted to confine 

 the psychology of the cell. We shall restrict our- 

 selves to the mention of one of these phenomena, to 

 show the complexity of the psychic life of micro-organ- 

 isms: it is the existence of a power of selection, exer- 

 cised either in the search for food, or in the manoeu- 



