THE INSTINCTS OF ANIMALS 143 



instinctive actions, and in these the completion of one action is 

 obviously the stimulus to the second, the completion of the second 

 to the third, and so on, until the entire chain of inter-dependent 

 movements which make up the whole performance has been com- 

 pleted. 



Instincts have thus a material basis in the cells and fibres of the 

 nervous system, and through variations in the connexions and 

 irritability of these nervous parts they too can be modified, like any 

 of the other characters of the body, such as form and colour. 



Conscious actions depend directly on the will, and they have 

 a close connexion with instinctive actions in as far as these also can 

 be controlled by the will, that is, can be set a-going or inhibited, and 

 also, on the other hand, in as far as purely voluntary actions may 

 become instinctive through frequent repetition. The first case is 

 illustrated, for instance, when the suckling of a child at the mother's 

 breast is continued into the second year of life, as not infrequently 

 happens in the southern countries of Europe. Such a child knows 

 exactly why it wants the breast, and its action is a conscious one, 

 while the newborn child seeks about with the mouth instinctively, 

 and when it has found what it sought performs the somewhat complex 

 sucking movements automatically. The second case is illustrated, 

 when, for instance, we have made a habit of winding up a watch 

 on going to bed, and do it when we happen to change our clothes 

 through the day, although it is then purposeless and would have been 

 omitted if the action had required a conscious eff'ort of will. One can 

 often observe on oneself in how short a time a conscious action may 

 become instinctive. I once sent my keyless watch to a watchmaker 

 for repairs, and received from him for the time an ordinary watch, 

 which had to be wound with a key, which key I kept for safety in 

 my purse. At the end of eight days I got back my own watch, and 

 on undressing the first night I found myself 'instinctively' taking 

 my purse from my pocket in order to get the key, which, as I very 

 well knew, I no longer needed. And that a long series of complex 

 movements, originally performed only consciously, may be gone 

 through instinctively, is shown by the fact that pieces of music 

 which have been learnt by heart can often be played without mistake 

 from beginning to end while the player is thinking of quite other 

 things. The complex instinctive actions of animals are performed in 

 quite a similar manner. 



There is thus no sharp boundary line between reflex and in- 

 stinctive actions, nor between instinctive and conscious actions, but 

 one passes over into the other, and the thought suggests itself, that in 



