Man and Microbes. 101 



Berlin in November, London during the middle of December, 

 and by the end of this month it had reached New York. The 

 duration of an epidemic in any one locality is about six weeks. 

 There is no disease of modern times that attacks indiscrim- 

 inately so large a portion of the inhabitants. Fortunately the 

 mortality is low. 



XVI. CARRIERS OF DISEASE. 



Already the relation of the bed bug to relapsing fever has 

 been mentioned. The flea has been convicted of inoculating 

 mankind with the black death. The cockroach, along with the 

 fly, is now being accused of being an active agent in promis- 

 cuously scattering the destructive seeds of typhoid fever and 

 tuberculosis. The stable fly is now being suspected of inoculat- 

 ing into man such grave diseases as infantile paralysis and 

 mening'itis. 



Certain insects, however, are responsible for dissemination 

 of specific microbes, and only through specific insects are cer- 

 tain diseases contracted. For example, it is through the me- 

 dium of the louse alone that the disastrous typhus fever attacks 

 man. Likewise the fatal Rocky Mountain spotted fever of 

 Montana can be contracted only through the bite of the tick. 



In the war on, and subjugation of, the pathogenic microbes, 

 the destruction of these carriers is as eflficacious in the elimina- 

 tion of a disease as is the destruction of the germ itself. Two 

 noteworthy diseases, malaria and yellow fever, which have pro- 

 foundly affected the activities of man, are now being van- 

 quished as a result of war against the carriers. 



Malaria is due to an animal microorganism, discovered by 

 Laveran in 1880, which enters the red blood cells and there 

 saps out the function and vitality of these important cells. 

 How these devitalizing protozoan organisms gained entrance 

 into the blood stream was an important and perplexing prob- 

 lem. This was finally settled by Major Ross, of the English 

 army, who demonstrated that a certain genus of mosquito — • 

 Anopheles — was responsible for injecting the microbes into 

 man. This mosquito imbibes the protozoan from marshes or 

 infected blood, and it then lives and multiplies in the intestines 

 of the mosquito after which it is inoculated into man when the 

 mosquito sucks its diet of blood. 



To prove that the Anopheles is responsible for malaria, men 



