4 8 THE POPULAR SCIENCE MONTHLY 



mals contained plague microbes. Fleas attacking rats were then sus- 

 pected, and experiments proved that they were capable of transmitting 

 the disease to human beings. Rats and ground squirrels die in large 

 numbers from the plague/ 6 which is said to be primarily a disease of 

 rats. 



So, working in the light of the knowledge previously gained, Dr. 

 Blue, of the Public Health and Marine Hospital Service, in charge of 

 the outbreak of plague in San Francisco in 1907, directed the warfare 

 against rats, killing more than a million in the city, and disinfecting 

 them as soon as they could be caught. At first the work was difficult. 

 Cases of plague were kept secret. The prejudices of ignorance and 

 superstition had to be overcome. City officials as well as the people had 

 to be educated, and laws made and enforced. But the work was finally 

 performed so thoroughly that San Francisco made a new record in 

 sanitation, and only about 140 cases developed. Except for this effec- 

 tive campaign not only San Francisco and California were endangered, 

 but the whole country imperiled. 17 



Remedial Measures 



Destroy all rats by the use of baited traps and poisons, dipping them 

 immediately in a solution of corrosive sublimate to disinfect them. 

 This immediately kills the rats and the fleas, with the plague germs on 

 them. 



Fumigate buildings to kill fleas and disease germs. 



Build solid concrete foundations, floors and walls where possible in 

 buildings and wharves to keep out rats. 



Other Diseases that are Known or Thought to be Transmitted 



by Insects 



There are certain other diseases, mostly tropical, that are known to 

 be carried by insects, and still others that are believed to be similarly 

 transmitted, though the connecting evidence forming the proof is not 

 yet complete. Elephantiasis is caused by worm-like parasites trans- 

 mitted through the bites of certain mosquitoes of the genus Culex in 

 the East and West Indies. Dengue fever and malta fever are probably 

 disseminated by mosquitoes. 



It is thought that the germs of leprosy are transmitted by the bites 

 of mosquitoes, flies, fleas, lice, mites or bedbugs. Dr. Patton, of the 

 Indian Medical Service, has demonstrated that the fatal and infectious 

 tropical disease called " kala-azar " is transmitted by the bites of the 



18 E. W. Doane, "Insects and Disease," p. 155. 



17 Eeport of Citizens ' Health Committee, ' ' Eradicating Plague in San 

 Francisco. ' ' 



18 R. W. Doane, "Insects and Disease," p. 173. 



