176 



CIVIC BIOLOGY 



alone. One half the people of Italy were killed by it. Whole 

 villages and towns were left without a living inhabitant, and 

 cattle ranged at will among the unharvested fields. In the 

 recent epidemic it is estimated that the plague has killed in 

 India, up to 1907, no less than 5,250,000. It has gained a 

 foothold in this country, but San Francisco, in the most thrill- 

 ingly interesting civic effort ever recorded in human history, 

 and with the best assistance the national government could 



give, stamped it out after 



taking a meager toll of 

 seventy-seven lives. 



* He died of the plague and 

 all my family with him. I have 

 no home or wife or relation to 

 go to so I will take no leave this 

 year." Reply of a native sol- 

 dier in India to a question about 

 his brother. 



Bubonic plague in man is 

 entirely dependent on the dis- 

 ease in the rat. 



The infection is conveyed 

 from rat to rat and from rat to 

 man solely by means of the rat flea. Lantz, quoted from " Etiology 

 and Epidemiology of Plague," p. 93. Calcutta, 1900 



FIG. 85. Lead pipe gnawed by rats 



This flooded a house and fortunately caused 

 only $7 damage 



Thus a bacterium, an insect, a mammal, and man are 

 bound together in a biological relation which has cost the 

 world hundreds of millions of human lives and centuries of 

 misery and horror. At last modern biology has discovered 

 this relation, and the fact that an intelligent people can learn 

 and realize its truth and act together for the common good has 

 made the difference between the San Francisco epidemic and 

 that of India 77 lives to 5,250,000. If the rat did no other 

 damage, is not this sufficient reason to induce every citizen of 

 a civilized community to exterminate rats from his premises ? 



