INTRODUCTION 7 



cause of the downfall of prehistoric American civiliza- 

 tions, while a number of writers are convinced that an 

 unprecedented era of progress is now facing Latin Amer- 

 ica, due primarily to the conquest of that dread disease. 



If the world had had biological workers years ago 

 who were able to prevent cancer, so that the father of 

 William II had not died within three months after 

 ascending the German throne, all Europe might have 

 been different from what it is. 



Biological workers may rightfully claim to have in- 

 fluenced the world a thousandfold more than rulers and 

 warriors, for this latter group has largely been given to 

 destruction, while the work of the biologist aims to be 

 constructive. Generations now unborn will profit by his 

 work. His efforts become increasingly interesting and 

 vitally important, and, being concerned with life in all 

 its ramifications, his field is inexhaustible. 



The combined and coordinated efforts of a great many 

 separate workers, scattered through many lands, usually 

 are necessary to bring a scientific idea to full fruition. 

 This is well shown in the work on tjrphoid fever, a dis- 

 ease of especial interest to you who have so many typhoid- 

 endemic centers. 



Huxham, as long ago as 1737, described the difference 

 between typhoid and typhus fevers, although it took 

 nearly a hundred years before a careful study of the actual 

 lesion (not the external symptoms) brought forth the 

 true difference and relationships of the two. Wm. Gerhard, 

 of Philadelphia, established this difference and relation- 



