122 PHYSIOLOGY. 



Disease Germs. But there are floating in the air many 

 kinds of spores that may grow in our bodies. We know 

 that many of our contagious diseases are due to the growth 

 in our bodies of some of these spores. Our bodies are a 

 good soil for certain germs. The germs that cause con- 

 sumption, typhoid fever, Asiatic cholera, erysipelas, diph- 

 theria, and some forms of blood poisoning are well known. 

 Microscopists know them when they see them as readily 

 as we know peas from beans. And it is proved beyond 

 all doubt that these germs get into our bodies by being 

 breathed in, or by being eaten in food, or in drinking 

 water, or by introduction into the blood in wounds. We 

 have reason to believe that smallpox, yellow fever, measles, 

 and scarlatina are caused by germs, but these diseases have 

 not been studied so successfully. 



How to avoid Germs. How can we avoid or get rid 

 of dusts of these kinds ? To exterminate any plant, we 

 try to keep the seeds from ripening, and to kill all that do 

 ripen. Let us take a case that, while not pleasant to con- 

 template, is too terribly true to allow of being called an 

 imagined case. 



The Danger from Consumption. A consumptive ex- 

 pectorates on the pavement. In this sputum are probably 

 hundreds, if not thousands, of germs known as bacilli 

 {Bacillus tuberculosis}. They are alive. Now, so long as 

 they remain on the pavement they do no harm. The 

 sputum dries. But the bacilli are not killed by drying. 

 With other dry material from the pavement they form 

 part of the common dust. Any one of us may breathe 

 some of this kind of matter any day, for there are persons 

 afflicted with this dreaded disease in every community. 

 Our bodies furnish the very best soil for the germs. We 



