174 BIOLOGY: GENERAL AND MEDICAL 



former attempts and modifies its behavior so as to over- 

 come the difficulties in the way of performance, and finally 

 wins its way to success through improvement of the method, 

 does not know what it is doing. 



Knowledge of what one is doing is consciousness, and 

 we next pause to inquire how it fits in with the general 

 views of the functions of the nervous system already ad- 

 vanced. 



Consciousness. As it was impossible to find the thresh- 

 old of the various manifestations of nervous energy that 

 have been considered, so it is impossible to say at what 

 point in the development of the nervous system conscious- 

 ness makes its appearance. Shall it be imagined that the 

 protozoa, in whose protoplasm we find the foreshadowings 

 of most specialized functions, are consciousness? Surely 

 not. It is only necessary to reflect upon the succession of 

 reflex activities that go on inside of us all the time, govern- 

 ing the activities of our internal organs, maintaining and 

 timing the respiratory movements, the cardiac movements, 

 the digestive activities, etc., to realize that they take 

 place entirely independently of our consciousness. Muscle 

 reflexes maintain our balance and regulate our posture 

 every moment without consciousness on our part. De- 

 fensive reflexes now and then surprise us as we become 

 conscious of them after the acts themselves have been 

 performed. The frog with its brain destroyed leaps from 

 the hot water into which it is thrown or wipes away the 

 acid applied to one leg by skilful movements of the other 

 leg without the least possibility of knowing what it is 

 doing. The brainless pigeon thrown into the air flies to 

 a convenient perch and comes to rest without knowing 

 what has happened. 



Even in our own normal bodies the most complex 

 activities sometimes result from automatic activities 

 without consciousness, as when one walks and talks in 

 his sleep, or continues to play complicated music involving 

 difficult technic while looking away from the piano and 

 talking about something else. 



