450 GENERAL ZOOLOGY 



teenth century. There are evidences that a rather high type 

 of civilization flourished on this continent at an early period, 

 but when the white settlers first arrived they found the 

 Indians in a stage of development which is commonly called 

 the Stone Age. This means that they formed stones into 

 spearheads and arrowheads by chipping off pieces until the 

 desired shape was attained. Weapons and most of the 

 implements which they used were formed in this way. In 

 some instances they had discovered how to use metal for 

 making implements and decorations, but stone was the 

 common material for all such purposes. 



In Europe and Asia modern civilization was established 

 long before it was in America. Yet even in these countries 

 many remains of primitive man are still found. In the caves 

 where men dwelt before they began to build shelters of their 

 own many stone implements similar to those found in 

 America have been discovered. Objects of the same sort 

 found in the gravel deposits along streams give evidence 

 that these early implements date from a time during or 

 just following the geological period known as the Ice Age. 

 These oldest signs of man's occupation of the earth are 

 thought to date back several hundred thousand years. 



It is only a few hundred years since superstition and 

 magic played the greatest role in human thinking. Even 

 as recently as two or three generations ago the causes of 

 disease were attributed to evil spirits, as they still are by 

 uncivilized tribes at the present day. The unknown to 

 these people was shrouded in mystery. No attempt was 

 made to understand what was not known. Though there 

 are many things of which we today are still ignorant, we 

 do not look upon many of these as unknowable. Much of 

 this change in our attitude is due to the influence of science 

 upon our thinking. Our highly trained physician with his 

 laboratory for discovering the cause of disease has replaced 



