Flowerless-Plant Study 723 



>1 



/. Cholera bacillus. 4. Bacteria from tubercle on white sweet 

 2. Typhoid bacillus. clover, much enlarged, 



j. A bacillus found in sewage. 5 and 6. Bacteria of lactic acid ferments 

 These are all enlarged 2000 times. in ripening of cheese, much enlarged. 



BACTERIA 



Teacher's Story 



The yellow, pink or purple spots developed upon the moist and moldy 

 bread are caused by bacteria and yeast. Bacteria are one-celled organ- 

 isms now classed as plants ; they are the smallest known living beings, and 

 can only be seen through a high power microscope. 



Bacteria grow almost everywhere in the soil, on all foods and fruits, 

 in the water of ponds, streams and wells, in the mouths and stomachs of 

 human beings, and in fact in almost all possible places, and occur in the 

 air. Most of them are harmless, some of them are useful, and some pro- 

 duce disease in both plants and animals, including man. 



What bacteria do would require many large volumes to enumerate. 

 Some of them develop colors or pigments; some produce gases, often ill- 

 smelling; some are phosphorescent; some take nitrogen from the air 

 and fix it in the soil; some produce putrefaction; and some produce 

 disease. Nearly all of the "catching diseases" are produced by bacteria. 

 Diphtheria, scarlet fever, typhoid fever, consumption, influenza, grippe, 

 colds, cholera, lockjaw, leprosy, blood poisoning and many other diseases 

 are the result of bacteria. On the other hand, many of the bacteria are 

 beneficial to man. Some forms ripen the cream before churning, others 

 give flavor to butter; while some are an absolute necessity in making 

 cheese. The making of cider into vinegar is the work of bacteria ; some 

 clear the pollution from ponds and streams; some help to decompose the 

 dead bodies of animals, so that they return to the dust whence they came. 



We have in our blood little cells whose business it is to destroy the 

 harmful bacteria which get into the blood. These little fighting cells 

 move everywhere with our blood, and if we keep healthy and vigorous by 

 right living, right food and exercise, these cells may prove strong enough 

 to kill the disease germs before they harm us. Direct sunlight also kills 

 some of the bacteria. Seven or eight minutes exposure to bright sunlight 

 is said to kill the germs of tuberculosis. Exposure to the air is also a help 

 in subduing disease germs. Bichloride of mercury, carbolic acid, formal- 

 dehyde and burning sulphur also kill germs, and may be applied to cloth- 

 ing or to rooms in which patients suffering from these germ diseases have 

 been. We can do much to protect ourselves from harmful bacteria by 

 being very clean in our persons and in our homes, by bathing frequently 

 and washing our hands with soap often. We should eat only pure and 

 freshly cooked food, we should get plenty of sleep and admit the sunlight 

 to our homes ; we should spend all the time possible in the open air and be 

 careful to drink pure water. If we are not sure that the water is pure, it 

 should be boiled for twenty minutes and then cooled for drinking. 



In Experiment A the milk vials and the corks are all boiled, so that 

 we may be sure that no other bacteria than the ones we chose are present, 



