WHAT IS PHYSICAL LIFE 



sects. Thus the organism of ague or ma- 

 larial fever, and the yellow fever thing, 

 come through hypodermic injection into 

 us by two separate varieties of mosquitoes. 

 None of the one hundred and twenty-three 

 remaining varieties of mosquitoes do more 

 than sing and sting. The terribly mortal 

 , disease of Eastern India, called Kala azar, 

 which destroys ninety-eight per cent, of 

 those attacked, comes by the bites of bed- 

 bugs. But a special interest attaches to 

 the fatal Sleeping Sickness of Africa, as 

 that is due to the bite of the tsetze fly, 

 which harbors in its mouth species of pro- 

 tozoa called trympanosomes. This tsetze 

 fly is responsible not only for fearful hu- 

 man epidemics but for the destruction of 

 vast numbers of cattle, and also for the 

 deaths of some of the largest forms of 

 wild game in Africa. It is not improbable 

 that many of the earth's large animals now 

 extinct may have been killed off by similar 

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