216 



INTRODUCTION TO BOTANY 



FIG. 171. A chart illustrating the number of deaths from typhoid fever 



before, during, and after the introduction of improved systems of sewage 



disposal and water supply 



Five prominent cities of the world are selected. The figures indicate the num- 

 ber of deaths for each 10,000 inhabitants. Rearranged from a chart in Abbott's 

 "Hygiene of Transmissible Diseases" 



The house fly is a dangerous agent of distribution of typhoid 

 and probably of other disease bacteria. The atmosphere is an 

 efficient carrier of the bacteria of tuberculosis. Every possible 

 effort should be made to remove the breeding places of flies 



