CHAPTER IX 



THEIR RELATION TO MAN: AS CARRIERS 

 OF DISEASES 



SINCE the development and general acceptance of 

 the microbian or "germ" theory as applied to many 

 contagious and infectious diseases, and its absolute 

 demonstration in plagues like cholera, typhoid fever, 

 dysentery and other enteric or intestinal troubles, as 

 well as in consumption, pneumonia, diphtheria and other 

 affections of the respiratory organs, the question of the 

 agencies concerned in the distribution of these germs 

 has come to the front. 



The surgeon has long known that suppurations and 

 pus-producing inflammations might be carried from one 

 individual to another by almost any sort of carrier; so 

 when he operates, he sterilizes his instruments, his 

 hands, the cut or bruised surfaces, and protects the 

 wounds by antiseptic dressings. That flies were among 

 the agencies for spreading suppurations was soon 

 learned, and the readiness with which flies gather on 

 sores or raw surfaces is matter of common observation. 

 When it was observed that flies of various kinds gathered 

 with as much readiness on fecal or excrementitious 

 matters as on food products in the kitchen, and were 

 ready to change their diet from one to the other without 

 much provocation, the conclusion that they might inocu- 

 late the food products and through them healthy indi- 

 viduals from the fecal matter was not a difficult one 

 to draw. 



In the cholera epidemic at Hamburg not so many 

 years' ago, this was absolutely demonstrated as to that 



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