PARASITOLOGY 



PART I 

 MEDICAL ENTOMOLOGY 



INSECTS AND DISEASE 



DISCUSSION 

 HOW PATHOLOGICAL CONDITIONS ARE PRODUCED 



General considerations. By pathological conditions we 

 would have understood a diseased state of tissue, deranged 

 function or the like, an abnormal condition of the body. Ani- 

 mal diseases may be produced in many ways, and it is not the 

 object of this exercise to give a complete discussion of even the 

 general principles of pathology, except only in so far as insects 

 are concerned. In this work we cannot merely define those in- 

 sects as parasites in the usual acceptance of the term as defined 

 by Braun, "living organisms which take up their abode, for the 

 purpose of procuring food, temporarily or permanently, on or 

 within other living organisms," because there are certain insects 

 which are not usually considered as parasites, but are never- 

 theless the grossest transmitters of diseases, e. g. the housefly, 

 as a transmitter of certain enteric affections. 



Insects and arachnids may relate to pathological conditions, 

 whether serious or of little consequence, in one or more of the 

 following ways, first, through direct infection, second, through 



