246 DEVELOPMENT AND HEREDITY. 



in order to develop ; and the degree of development 

 which they attain is greater as the number and 

 variety of the stimuli increase. 



In the lives of human beings, at periods when 

 the intensity of the general stimuli to life and 

 action is greatly increased, there is a corresponding 

 increase in the emotional or bodily activity result- 

 ing in a change of bodily conditions or a change 

 of character. The history of nations shows certain 

 periods when the imagination has been strongly 

 stimulated by the infusion of new ideas from abroad, 

 or by ideas evolved at home, or by great discoveries, 

 so that for a few generations the material and 

 intellectual activity of the people has displayed 

 wonderful vigour, — the unusually strong stimulus 

 thus making an epoch of greatness in the life of 

 the nation, far above the average level of the national 

 existence. As examples of ideas or events which 

 have exerted a profound stimulus upon the life of 

 nations, may be mentioned Mohammedanism among 

 the Saracens, the crusades preached by Peter the 

 Hermit, the introduction in Europe of the art of 

 printing, the revival of classic learning, and the 

 discovery of the new world. Geographical position, 

 the opening of new routes of trade, civil and foreign 

 wars, have also had their effect in promoting 

 suddenly the intellectual and moral development 



