BACTERIA AND DISEASE 321 



their patients free from bacterial infection. All instru- 

 ments used are carefully sterilized and everything con- 

 nected with the operation is made scrupulously clean. 

 As a result operations are now performed which were un- 

 dreamed of before the days of aseptic and antiseptic sur- 

 gery, and the number of infections following ordinary op- 

 erations has been greatly diminished. 



Cuts, scratches and abrasions of the skin, while they 

 usually heal up with no serious results, may become in- 

 fected and lead to blood poisoning. It is well to wash 

 them, therefore, with peroxide of hydrogen or some other 

 antiseptic, and then bind them up so as to exclude the 

 entrance of other germs. Boils and carbuncles result from 

 bacterial infection and the pus they contain may give rise 

 to similar infections in other parts of the body, or in the 

 body of another person. The common notion that boils 

 are useful in eliminating impurities from the blood is 

 absurd. On the contrary they are a source of actual poi- 

 soning to the whole body. 



The number of diseases caused by bacteria and protozoa 

 is very great. We shall describe, therefore, only a few of 

 those about which everyone should have some knowledge 

 for the sake of his own safety. 



Colds. What we commonly call colds are really infec- 

 tions. Almost everyone has noticed how colds tend to 

 run through a family or a school, and how at times colds 

 are unusually prevalent. People commonly believe that 

 they " catch cold" by sitting in a draught, getting their 

 feet wet, or exposing themselves in cold weather. What 

 really happens is that their temperature or their resistance 

 may be reduced by these circumstances, and thus an op- 

 portunity is offered for the germs of the infection to make 

 headway, whereas otherwise they might have been kept 



in abeyance. Arctic travellers and people living away 

 21 



