HEALTHY BODIES AND BACTERIA 



351 



Finally comes Koch, who discovered a way of separating 

 bacteria so that each kind may be studied by Itself, a 

 method called getting a "pur.' culture," and who aJ 

 invented the tuberculin test. Most of our facts about 



bacteria have been learned during the past thirty-fi 

 years. 



248. Healthy Bodies and Bacteria. — So much has been 

 said about harmful bacteria that a word of caution is 

 needed. Two facts should 

 make us take a sane view of 

 the situation : (1) for every 

 harmful bacterium there are 

 thousands of helpful ones ; and 

 (2) harmful ones cannot do 

 their work, or even live, in a 

 perfectly healthy body, for such 

 a body is constantly preparing 

 a substance (antitoxin) which 

 neutralizes the bacterial poison 

 (toxin). Our chief aim, then, 

 should be to keep well, and a few 



simple rules of hygiene will accomplish this. (1) Spend 

 as much time as possible exercising in the open air. 

 (2) Sleep as many as eight hours out of twenty-four in 

 a well-ventilated room or out of doors. (3) Bat only 

 food which agrees with you, and not too much <d that. 

 (4) Wear seasonable clothing. (5) Keep the skin clean 

 through frequent bathing. (6) Have a definite occupa- 

 tion, work faithfully at it, do your best, and don't worry. 



Figure 372. — Beef Jelly. 

 Exposed in unsanitary dairy. 



SUMMARY 



The smallest and simplest of all the plants are the 

 bacteria. Most of them are helpful, ridding the earth of 

 waste material, giving flavor to food, gathering nitrogen 



