INTRODUCTION 9 



objected that in taking up this attitude we had left out of account one 

 supreme fact, viz. the existence of consciousness in ourselves. As a com- 

 parative and objective study, however, physiology is concerned, not with 

 the study of consciousness, but with the conceptions in consciousness of the 

 phenomena presented by living beings. Consciousness, in fact, we know only 

 in ourselves. From the actions of other living beings similarly organised, we 

 infer in them the existence of a similar consciousness. Again, from the fact 

 that the reactions of the higher mammals are evidently determined, not by 

 immediate impressions, but largely by stored-up impressions of past stimuli, 

 we credit them also with a certain but lower degree of consciousness. As 

 we descend the scale of animal life, evidence of the existence of consciousness, 

 as we know it, rapidly diminishes and finally disappears, though it is im- 

 possible to draw a sharp line between those animals which possess conscious- 

 ness and those in which it is absent. That it is a necessary accompaniment 

 of life is certainly not the case. A man is living though he is asleep, anaes- 

 thetised, or stunned, and it would be absurd to speak of the consciousness 

 of a cabbage. Consciousness is, in fact, connected with the possession of a 

 highly developed central nervous system, and its activity is in proportion to 

 the complexity of this system. Since the brain with all the other organs 

 of the body is derived from a simple cell, the fertilised ovum, similar in its 

 absence of differentiation to the lowest organisms, it might be argued that all 

 types of life are endowed with something which is not consciousness, but 

 which has the potentiality of developing into consciousness. To such a 

 hypothetical property Lloyd Morgan has given the name ' metakinesis.' We 

 have, however, no means of judging of the presence or absence of this hypo- 

 thetical quality and still less of determining whether it is a property only of 

 living substance, or is shared also by the atoms of so-called dead material. 



