10 PHYSIOLOGY 



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 con- 

 sciousness. 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 impossible to draw a sharp line between 

 those animals which possess consciousness 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, anaesthetised, 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 hypothetical 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. Moreover, 

 since this hypothetical quality does not claim to be a form of energy, 

 it need not trouble us in our study of the energy-changes in the body 

 and the conditions which determine them. 



