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THE AMERICAN MUSEUM JOURNAL 



insects; so the seasonal prevalence proves nothing by itself. Another 

 curious fact brought out in the Massachusetts studies by Richardson how- 

 ever was the greater proportionate incidence of infant paralysis in rural 

 than in urban districts. Again the rule is not a universal one, but the fact 

 that even in one state a distinctly higher percentage of cases occurred in the 

 country than in the city was a striking one. Diseases that spread directly 

 from person to person are almost always most prevalent where persons 



Wing of the house fly (Musca domestica) above and of the stable fly (Stomoxys calci- 

 trans) below. Note the sharp elbow in the third long wing vein of Musca and the less bent 

 vein of Stomoxys. Drawing by Ignaz Matausch 



congregate so that the opportunities for contagion are most frequent; while 

 insect-borne diseases are often most serious in the country where insect 

 breeding places are more frequent. 



These facts led the Massachusetts investigators to search with special 

 care for a connection between some insect host and the prevalence of infant 

 paralysis, and in 1910 Dr. P. A. E. Sheppard, working for the state health 

 department, noted the large number of cases in which fly bites were reported 



