INSTINCTS 247 



the result of use (exercise) or disuse. It is for this reason that 

 habits acquired in youth are most lasting, and it is for this 

 reason that " you cannot teach an old dog new tricks." Things 

 that " come natural " to us early in life become difficult if they 

 are not practiced ; tricks that we learn in our youth are for- 

 gotten if not practiced. Thus we may lose instincts and out- 

 grow them ; or we may fix them in our ways of life, remaining 

 childish though old in years. 



