CHAPTER I. 

 INTRODUCTION 



EARLY SUGGESTIONS REGARDING THE TRANSMISSION OF DISEASE 



BY INSECTS 



Until very recent years insects and their allies have been considered 

 as of economic importance merely in so far as they are an annoyance 

 or direct menace to man, or his flocks and herds, or are injurious to 

 his crops. It is only within the past fifteen years that there has 

 sprung into prominence the knowledge that in another and much more 

 insiduous manner, they may be the enemy of mankind, that they 

 may be among the most important of the disseminators of disease. 

 In this brief period, such knowledge has completely revolutionized 

 our methods of control of certain diseases, and has become an import- 

 ant weapon in the fight for the conservation of health. 



It is nowhere truer than in the case under consideration that how- 

 ever abrupt may be their coming into prominence, great move- 

 ments and great discoveries do not arise suddenly. Centuries ago 

 there was suggested the possibility that insects were concerned with 

 the spread of disease, and from time to time there have appeared keen 

 suggestions and logical hypotheses along this line, that lead us to 

 marvel that the establishment of the truths should have been so long 

 delayed. 



One of the earliest of these references is by the Italian physician, 

 Mercurialis, who lived from 1530 to 1607, during a period when 

 Europe was being ravaged by the dread "black death", or plague. 

 Concerning its transmission he wrote : ' ' There can be no doubt that 

 flies feed on the internal secretions of the diseased and dying, then, 

 flying away, they deposit their excretions on the food in neighboring 

 dwellings, and persons who eat of it are thus infected." 



It would be difficult to formulate more clearly this aspect of the 

 facts as we know them to-day, though it must always be borne in 

 mind that we are prone to interpret such statements in the light of 

 present-day knowledge. Mercurialis had no conception of the animate 

 nature of contagion, and his statement was little more than a lucky 

 guess. 



Much more worthy of consideration is the approval which was 

 given to his view by the German Jesuit, Athanasius Kircher in 1658. 



