236 



CIVIC BIOLOGY 



Germs circulating- in the blood are usually drawn off by 

 blood-sucking insects, ticks, or mites ; malaria and yellow 

 fever, by mosquitoes ; typhus fever, by body lice (and per- 

 haps by fleas and bedbugs); plague, by fleas (possibly also 

 leprosy) ; typhoid, by bedbugs ; Texas fever and spotted 

 fever, by ticks; infantile paralysis (?) and anthrax, by the 



Micrococci 



Bacilli 



Inflammation 



f Pneumonia, 



Mheumatism, 



Sores, Boils) 



Diphtheria 



FIG. 109. Pathogenic bacteria modeled to scale in plasticene (mirra = 

 centimeters), magnification of models being 10,000 diameters 



A suggestion for a laboratory collection. Mount in insect cases under glass. 

 Photograph by the author 



stable fly; and sleeping sickness, by one of the tsetse flies. 

 Diseases marked by lesions of the skin measles, scarlet fever, 

 smallpox, and probably dandruff and eczema may escape 

 with the scales of cuticle or the contents of blisters or sores. 

 How living disease bacteria are carried. The greatest barrier 

 to the learning of truth is apt to be a firm belief of an error. 

 No set of ideas has cost the world more misery, suffering, 

 and loss than false notions, prejudices, and superstitions re- 

 garding the transmission of diseases. First they were carried 



