312 



Constant Care Is Needed for Health umi" vi 



Bacillus coli (cyslilui) 



Eberlhella typhi 

 (typhoid) 



Streptococcus ot pus 



Bacilli 



Cocci 



Vibrio comma 

 (Aiiatic cholera) 



Spirilla 



Fk;. 287 (above) According to shape bacteria 

 are called bacilli, cocci {cock'sye) and spirilla. 

 How do these differ in shape? Some bacteria 

 hang together in chains or in small groups. 



they are considered plants. Ihcy have 

 no nucleus but do have chromatin gran- 

 ules scattered through the cytoplasm. 

 Some bacteria can move by means of 

 long hairlikc projections (flagella) but 

 most bacteria cannot carry on locomo- 

 tion. Drawings of several kinds of bac- 

 teria may be seen in Figure 287, magni- 

 fied about 3000 times. Because they all 

 lack chlorophyll they arc classified as 

 fungi along with mushrooms, molds, and 

 vcasts. Like other living cells they secrete 

 enzymes, digest, assimilate, release en- 

 ergy which the\' use, and reproduce. 



Fk;. 2H8 (left) This illustrates what may hap- 

 pen when a bacterium settles on a piece of 

 meat. Arrows indicate that something is leav- 

 ing and something is entering the bacterium. 

 Can you explain what? Drawing B represents 

 the same piece of meat some time later. What 

 has happened to the bacterimn and to the meat? 

 What w-ould be the last chapter of this story? 



The study of bacteria. The study of 

 bacteria, bacteriology , includes observa- 

 tion of the growth of bacteria in the 

 laboratory', their effect on other organ- 

 isms, and their appearance under the 

 microscope. Bacteriology is a young sci- 

 ence because methods of raising bacteria, 

 microscopes good enough to see them, 

 and special methods of making them vis- 

 ible under the microscope were not dis- 

 covered until after the middle of the last 

 century. 



Present tuethods make ciiltiiring (rais- 

 ing) most kinds of bacteria easy. In the 



1, 



