A HISTORY OF SCIENCE 



ent-day speech is still reminiscent of this ; as when, for 

 example, we speak of an ''attack of fever," and the 

 like. 



When, following out this idea, we picture to our- 

 selves the conditions under which primitive man lived, 

 it will be evident at once how relatively infrequent 

 must have been his observation of what we usually 

 term natural death. His world was a world of strife ; 

 he lived by the chase ; he saw animals kill one another ; 

 he witnessed the death of his own fellows at the hands 

 of enemies. Naturally enough, then, when a member 

 of his family was "struck down" by invisible agents, 

 he ascribed this death also to violence, even though 

 the offensive agent was concealed. Moreover, having 

 very little idea of the lapse of time being quite un- 

 accustomed, that is, to reckon events from any fixed 

 era primitive man cannot have gained at once a clear 

 conception of age as applied to his fellows. Until a 

 relatively late stage of development made tribal life 

 possible, it cannot have been usual for man to have 

 knowledge of his grandparents; as a rule he did not 

 know his own parents after he had passed the adolescent 

 stage and had been turned out upon the world to care 

 for himself. If, then, certain of his fellow - beings 

 showed those evidences of infirmity which we ascribe 

 to age, it did not necessarily follow that he saw any 

 association between such infirmities and the length of 

 time which those persons had lived. The very fact 

 that some barbaric nations retain the custom of killing 

 the aged and infirm, in itself suggests the possibility 

 that this custom arose before a clear conception Jiad 

 been attained that such drags upon the community 



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